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Lambda calculus

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encoded in the lambda calculus in size linearly proportional to the size of the Turing machine. The true cost of reducing lambda terms is not due to β-reduction per se but rather the handling of the duplication of redexes during β-reduction. It is not known if optimal reduction implementations are reasonable when measured with respect to a reasonable cost model such as the number of leftmost-outermost steps to normal form, but it has been shown for fragments of the lambda calculus that the optimal reduction algorithm is efficient and has at most a quadratic overhead compared to leftmost-outermost. In addition the BOHM prototype implementation of optimal reduction outperformed both
15978: 11314: 10939:, the existence of lambda terms which grow exponentially in size for each β-reduction. The result gets around this by working with a compact shared representation. The result makes clear that the amount of space needed to evaluate a lambda term is not proportional to the size of the term during reduction. It is not currently known what a good measure of space complexity would be. 13118:
Some other systems use juxtaposition to mean application, so 'ab' means 'a@b'. This is fine except that it requires that variables have length one so that we know that 'ab' is two variables juxtaposed not one variable of length 2. But we want to labels like 'firstVariable' to mean a single variable,
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reduces all computations with the same label in one step, avoiding duplicated work, but the number of parallel β-reduction steps to reduce a given term to normal form is approximately linear in the size of the term. This is far too small to be a reasonable cost measure, as any Turing machine may be
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would take the form of a collection of previously defined functions, which as lambda-terms are merely particular constants. The pure lambda calculus does not have a concept of named constants since all atomic lambda-terms are variables, but one can emulate having named constants by setting aside a
5739:. Under this view, β-reduction corresponds to a computational step. This step can be repeated by additional β-reductions until there are no more applications left to reduce. In the untyped lambda calculus, as presented here, this reduction process may not terminate. For instance, consider the term 6028:
Another aspect of the untyped lambda calculus is that it does not distinguish between different kinds of data. For instance, it may be desirable to write a function that only operates on numbers. However, in the untyped lambda calculus, there is no way to prevent a function from being applied to
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The leftmost innermost redex is reduced first. As a consequence, a function's arguments are always reduced before they are substituted into the function. Unlike normal order reduction, applicative order reduction may fail to find the beta-normal form of an expression, even if such a normal form
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for computation which are useful for formally studying properties of computation. The lambda calculus incorporates two simplifications that make its semantics simple. The first simplification is that the lambda calculus treats functions "anonymously;" it does not give them explicit names. For
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Like applicative order, but no reductions are performed inside abstractions. This is similar to the evaluation order of strict languages like C: the arguments to a function are evaluated before calling the function, and function bodies are not even partially evaluated until the arguments are
8908:. Lambda calculus cannot express this: all functions are anonymous in lambda calculus, so we can't refer by name to a value which is yet to be defined, inside the lambda term defining that same value. However, a lambda expression can receive itself as its own argument, for example in  2019:
Nothing else is a lambda term. That is, a lambda term is valid if and only if it can be obtained by repeated application of these three rules. For convenience, some parentheses can be omitted when writing a lambda term. For example, the outermost parentheses are usually not written. See
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Therefore, both strongly normalising terms and weakly normalising terms have a unique normal form. For strongly normalising terms, any reduction strategy is guaranteed to yield the normal form, whereas for weakly normalising terms, some reduction strategies may fail to find it.
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The fact that lambda calculus terms act as functions on other lambda calculus terms, and even on themselves, led to questions about the semantics of the lambda calculus. Could a sensible meaning be assigned to lambda calculus terms? The natural semantics was to find a set
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As call by name (hence weak), but function applications that would duplicate terms instead name the argument. The argument may be evaluated "when needed," at which point the name binding is updated with the reduced value. This can save time compared to normal order
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is the definition of a function invoking itself. A definition containing itself inside itself, by value, leads to the whole value being of infinite size. Other notations which support recursion natively overcome this by referring to the function definition
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The leftmost outermost redex is reduced first. That is, whenever possible, arguments are substituted into the body of an abstraction before the arguments are reduced. If a term has a beta-normal form, normal order reduction will always reach that normal
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has also addressed this question in various public lectures. Scott recounts that he once posed a question about the origin of the lambda symbol to Church's former student and son-in-law John W. Addison Jr., who then wrote his father-in-law a postcard:
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Subsequently, in 1936 Church isolated and published just the portion relevant to computation, what is now called the untyped lambda calculus. In 1940, he also introduced a computationally weaker, but logically consistent system, known as the
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The precise rules for α-conversion are not completely trivial. First, when α-converting an abstraction, the only variable occurrences that are renamed are those that are bound to the same abstraction. For example, an α-conversion of
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A paper giving a formal underpinning to the idea of 'meaning-is-use' which, even if based on proofs, it is different from proof-theoretic semantics as in the Dummett–Prawitz tradition since it takes reduction as the rules giving
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The examples 1 and 2 denote different terms, differing only in where the parentheses are placed. They have different meanings: example 1 is a function definition, while example 2 is a function application. The lambda variable
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for the lambda calculus is a bit tricky, because the cost of a β-reduction may vary depending on how it is implemented. To be precise, one must somehow find the location of all of the occurrences of the bound variable
9231:). The function does not need to be explicitly passed to itself at any point, for the self-replication is arranged in advance, when it is created, to be done each time it is called. Thus the original lambda expression 8759:. Because several programming languages include the lambda calculus (or something very similar) as a fragment, these techniques also see use in practical programming, but may then be perceived as obscure or foreign. 10609: 10507:
Whether a term is normalising or not, and how much work needs to be done in normalising it if it is, depends to a large extent on the reduction strategy used. Common lambda calculus reduction strategies include:
10431:) to denote anonymous function abstraction. In this context, types are usually objects of a syntactic nature that are assigned to lambda terms; the exact nature of a type depends on the calculus considered (see 4922: 9750:, every recursively defined function can be expressed as a lambda expression. In particular, we can now cleanly define the subtraction, multiplication and comparison predicate of natural numbers recursively. 8840:
By chaining such definitions, one can write a lambda calculus "program" as zero or more function definitions, followed by one lambda-term using those functions that constitutes the main body of the program.
567:). One reason there are many different typed lambda calculi has been the desire to do more (of what the untyped calculus can do) without giving up on being able to prove strong theorems about the calculus. 10435:). From a certain point of view, typed lambda calculi can be seen as refinements of the untyped lambda calculus but from another point of view, they can also be considered the more fundamental theory and 919: 5305: 5073: 4773: 2024:, below, for an explicit description of which parentheses are optional. It is also common to extend the syntax presented here with additional operations, which allows making sense of terms such as 3318: 5802: 5136:
In general, failure to meet the freshness condition can be remedied by alpha-renaming first, with a suitable fresh variable. For example, switching back to our correct notion of substitution, in
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The self-application achieves replication here, passing the function's lambda expression on to the next invocation as an argument value, making it available to be referenced and called there.
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Proceedings of the Joint Meeting of the Twenty-Third EACSL Annual Conference on Computer Science Logic (CSL) and the Twenty-Ninth Annual ACM/IEEE Symposium on Logic in Computer Science (LICS)
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This origin was also reported in . On the other hand, in his later years Church told two enquirers that the choice was more accidental: a symbol was needed and λ just happened to be chosen.
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datatypes, because a function is a first class datatype if and only if new instances of the function can be created at run-time. And this run-time creation of functions is supported in
6865:. Substitution on terms of the lambda calculus is defined by recursion on the structure of terms, as follows (note: x and y are only variables while M and N are any lambda expression): 2614: 4430: 3025: 2695: 1365: 1174: 1239: 1087: 987: 1691: 10935:
time cost model, that is, the reduction can be simulated on a Turing machine in time polynomially proportional to the number of steps. This was a long-standing open problem, due to
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The abstraction operator, λ, is said to bind its variable wherever it occurs in the body of the abstraction. Variables that fall within the scope of an abstraction are said to be
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Every recursively defined function can be seen as a fixed point of some suitably defined function closing over the recursive call with an extra argument, and therefore, using
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and other linguists' applications in the semantics of natural language, the lambda calculus has begun to enjoy a respectable place in both linguistics and computer science.
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languages can be understood in terms of the lambda calculus, which provides the basic mechanisms for procedural abstraction and procedure (subprogram) application.
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variable as the name of the constant, using abstraction to bind that variable in the main body, and apply that abstraction to the intended definition. Thus to use
2421: 1858:, that are defined by a certain formal syntax, and a set of transformation rules for manipulating the lambda terms. These transformation rules can be viewed as an 563:, it is a theorem that every evaluation strategy terminates for every simply typed lambda-term, whereas evaluation of untyped lambda-terms need not terminate (see 12079:. Parentheses can be dropped if the expression is unambiguous. For some applications, terms for logical and mathematical constants and operations may be included. 4125: 4003: 2063:
The focus of this article is the pure lambda calculus without extensions, but lambda terms extended with arithmetic operations are used for explanatory purposes.
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The syntax of the lambda calculus defines some expressions as valid lambda calculus expressions and some as invalid, just as some strings of characters are valid
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The second simplification is that the lambda calculus only uses functions of a single input. An ordinary function that requires two inputs, for instance the
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for programming languages; here typability usually captures desirable properties of the program, e.g. the program will not cause a memory access violation.
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This solves it but requires re-writing each recursive call as self-application. We would like to have a generic solution, without a need for any re-writes:
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Any redex can be reduced at any time. This means essentially the lack of any particular reduction strategy—with regard to reducibility, "all bets are off".
1527: 10887:, implying a time cost, or one must keep track of the locations of free variables in some way, implying a space cost. A naïve search for the locations of 10842:. Then he assumes that this predicate is computable, and can hence be expressed in lambda calculus. Building on earlier work by Kleene and constructing a 8142:
Then, with these two lambda terms, we can define some logic operators (these are just possible formulations; other expressions could be equally correct):
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covers lambda calculi from a practical type system perspective; some topics like dependent types are only mentioned, but subtyping is an important topic.
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By varying what is being repeated, and varying what argument that function being repeated is applied to, a great many different effects can be achieved.
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but lacks abstraction (except as part of the named constants, if these are considered non-atomic). This can also be viewed as anonymising variables, as
13255:; A note (accessed 2017) at the original location suggests that the authors consider the work originally referenced to have been superseded by a book. 3433:
are not alpha-equivalent, because they are not bound in an abstraction. In many presentations, it is usual to identify alpha-equivalent lambda terms.
551:. In typed lambda calculus, functions can be applied only if they are capable of accepting the given input's "type" of data. Typed lambda calculi are 11531: 15032: 10377:
combinator actually conflates two functionalities: rearranging arguments, and duplicating an argument so that it may be used in two places. The
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Second, α-conversion is not possible if it would result in a variable getting captured by a different abstraction. For example, if we replace
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were an early approach that traded this time cost for a quadratic space usage. More generally this has led to the study of systems that use
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As described above, having no names, all functions in the lambda calculus are anonymous functions. They only accept one input variable, so
7148: 13367: 4778: 3335:. It captures the intuition that the particular choice of a bound variable, in an abstraction, does not (usually) matter. For instance, 16014: 11919: 4432: ; a variable bound by an abstraction is not subject to substitution; substituting such variable leaves the abstraction unchanged 16488: 11615:, 58 (1936), pp. 345–363. This paper contains the proof that the equivalence of lambda expressions is in general not decidable. 8410:
make it convenient to write "if-then-else" expressions in lambda calculus. For example, the predecessor function can be defined as:
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Functional Programming Languages and Computer Architecture: 5th ACM Conference. Cambridge, MA, USA, August 26-30, 1991. Proceedings
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when working up to α-conversion (i.e. we consider two normal forms to be equal if it is possible to α-convert one into the other).
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passes the argument on to both subterms of the application, and then applies the result of the first to the result of the second.
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There are several notions of "equivalence" and "reduction" that allow lambda terms to be "reduced" to "equivalent" lambda terms.
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can be thought of as a function taking two natural numbers as arguments and returning a natural number; it can be verified that
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To substitute into an abstraction, it is sometimes necessary to α-convert the expression. For example, it is not correct for (λ
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of a term are those variables not bound by an abstraction. The set of free variables of an expression is defined inductively:
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Until the 1960s when its relation to programming languages was clarified, the lambda calculus was only a formalism. Thanks to
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reduction) captures the idea of function application. β-reduction is defined in terms of substitution: the β-reduction of (λ
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the question. This was historically the first problem for which undecidability could be proven. As usual for such a proof,
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is a free variable. Also a variable is bound by its nearest abstraction. In the following example the single occurrence of
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for lambda calculus. Many of these were originally developed in the context of using lambda calculus as a foundation for
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than the untyped calculus can. On the other hand, typed lambda calculi allow more things to be proven. For example, in
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Church's proof of uncomputability first reduces the problem to determining whether a given lambda expression has a
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In 2014, it was shown that the number of β-reduction steps taken by normal order reduction to reduce a term is a
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According to Scott, Church's entire response consisted of returning the postcard with the following annotation: "
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are alpha-equivalent lambda terms, and they both represent the same function (the identity function). The terms
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operations on them. In the simplest form of lambda calculus, terms are built using only the following rules:
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Biernacka, Małgorzata; Charatonik, Witold; Drab, Tomasz (2022). Andronick, June; de Moura, Leonardo (eds.).
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times and then applying it to zero. Exponentiation has a rather simple rendering in Church numerals, namely
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as a common means of evaluating lambda expressions and discusses the applicability of lambda calculus for
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By the way, why did Church choose the notation “λ”? In he stated clearly that it came from the notation “
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is a recent monograph that covers the main topics of lambda calculus from the type-free variety, to most
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function, can be reworked into an equivalent function that accepts a single input, and as output returns
587: 13059:. Studies in Logic and the Foundations of Mathematics. Vol. 103 (Revised ed.). North Holland. 12112:
For a full history, see Cardone and Hindley's "History of Lambda-calculus and Combinatory Logic" (2006).
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By convention, the following two definitions (known as Church Booleans) are used for the Boolean values
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To keep the notation of lambda expressions uncluttered, the following conventions are usually applied:
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are a fundamental concept within computer science and mathematics. The lambda calculus provides simple
611: 70: 11708:. A classic paper highlighting the importance of lambda calculus as a basis for programming languages. 2027: 532:. Its namesake, the Greek letter lambda (λ), is used in lambda expressions and lambda terms to denote 16589: 16539: 16301: 16190: 16000: 15958: 15907: 15804: 15302: 15263: 14740: 14385: 14065: 14060: 13872: 11933: 11701: 11432: 11338: 11332: 11224: 11092: 10490: 6355: 2515: 2429: 627: 498: 14414: 13562: 5450: 5318: 2827: 16705: 16649: 16508: 16087: 15799: 15729: 15268: 15120: 15103: 14826: 14306: 14048: 13072: 12496: 12301: 12225: 11905: 11893: 11881: 11869: 11506: 10832: 5731:
The lambda calculus may be seen as an idealized version of a functional programming language, like
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than the untyped lambda calculus, which is the primary subject of this article, in the sense that
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is reduced to itself by applicative order, while normal order reduces it to its beta-normal form
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is a syntactically valid term and represents a function that adds its input to the yet-unknown
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To Dissect a Mockingbird: A Graphical Notation for the Lambda Calculus with Animated Reduction
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The following predicate tests whether the first argument is less-than-or-equal-to the second:
6728:. Frequently, in uses of lambda calculus, α-equivalent terms are considered to be equivalent. 2470: 1738: 1453: 16569: 16463: 16428: 16316: 16291: 16135: 16052: 15851: 15704: 15496: 15214: 14950: 14856: 14715: 14700: 14581: 14556: 14096: 13428: 13143:, vol. 0804, Department of Mathematics and Statistics, University of Ottawa, p. 9, 12690: 11929: 11496: 11407: 11212: 10925: 10443: 10398: 7413: 4523: 4130: 2232: 1011: 730: 695: 13906: 13459: 10756:
of natural numbers is a computable function if and only if there exists a lambda expression
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will return a self-replicating lambda expression representing the recursive function (here,
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was supposed to be free but ended up being bound. The correct substitution in this case is λ
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Accattoli, Beniamino; Dal Lago, Ugo (14 July 2014). "Beta reduction is invariant, indeed".
13154: 11819: 11402: 11351: 11111: 11052: 10967:'s 1965 paper "A Correspondence between ALGOL 60 and Church's Lambda-notation", sequential 10737: 7158: 6170: 6085: 3252: 3111:', so functions may be used as the inputs, or be returned as outputs from other functions. 1893: 1315: 525: 58: 46: 14141: 13088: 12520: 12264: 12072:{\displaystyle (\lambda x.\lambda y.(\lambda z.(\lambda x.z\ x)\ (\lambda y.z\ y))(x\ y))} 11095:
property of the lambda calculus means that evaluation (β-reduction) can be carried out in
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which allows us to give perhaps the most transparent version of the predecessor function:
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is defined to be the identity function. Such repeated compositions (of a single function
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is used, then α-conversion is no longer required as there will be no name collisions. If
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combinators, equivalent to lambda calculus, but reducible without variable substitutions
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The above example is an expression that evaluates to a first-class function. The symbol
6018:{\displaystyle (\lambda x.xx)(\lambda x.xx)\to (xx)=(x)(x)=(\lambda x.xx)(\lambda x.xx)} 4257: 1991: 1968: 205: 16684: 16609: 16579: 16544: 16524: 16453: 16433: 16371: 16366: 16276: 16266: 16251: 16195: 15982: 15751: 15714: 15699: 15692: 15675: 15479: 15461: 15327: 15253: 15236: 15189: 15002: 14911: 14745: 14730: 14690: 14642: 14627: 14615: 14571: 14546: 14316: 14265: 14161: 14126: 13766: 13720: 13662: 13634: 13556:. Lecture Notes in Computer Science. Vol. 523. Springer-Verlag. pp. 289–312. 13424: 13390: 13187: 13144: 13033: 12946: 12938: 12900: 12859: 12817: 12775: 12738: 12584: 12576: 12416: 12396: 11937: 11900: 11771: 11378: 11367: 11319: 11249: 11107: 10980: 10614: 10470: 7162: 6819: 6773: 6626:, refers to subterms that can be reduced by one of the reduction rules. For example, (λ 5523: 5488: 5356: 5189: 4974:
For example, a substitution that ignores the freshness condition could lead to errors:
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The expression e can be: variables x, lambda abstractions, or applications —in BNF,
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are relevant. However, the lambda calculus does not offer any explicit constructs for
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As normal order, but computations that have the same label are reduced simultaneously.
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functions defined below, one can define a function that constructs a (linked) list of
1621:{\textstyle {\Bigl (}{\bigl (}x\mapsto (y\mapsto x^{2}+y^{2}){\bigr )}(5){\Bigr )}(2)} 821: 16664: 16619: 16599: 16559: 16498: 16468: 16448: 16241: 16170: 15977: 15917: 15724: 15534: 15524: 15416: 15297: 15132: 15108: 14889: 14873: 14778: 14755: 14632: 14601: 14566: 14461: 14296: 14166: 13804: 13652: 13575: 13478: 13438: 13339: 13206: 13060: 13003: 12975: 12724: 12696: 12666: 12639: 12478:, and compare to Moggi's calculus, and to Hasegawa's calculus. Conclusions on p. 111. 11843: 11811: 11788: 11726: 11635: 11580: 11539: 11501: 11313: 11274: 11048: 10655:
Like normal order, but no reductions are performed inside abstractions. For example,
10482: 10382: 10070: 8748: 7489: 7132: 7071: 7055:
For example, assuming some encoding of 2, 7, ×, we have the following β-reduction: (λ
6574: 3144: 3068: 1859: 1823: 1497: 13785: 13666: 13394: 13174:(1988). "A Proof-Theoretic Account of Programming and the Role of Reduction Rules". 12950: 11775: 11674: 16669: 16594: 16483: 16261: 15931: 15926: 15819: 15776: 15598: 15559: 15554: 15539: 15365: 15322: 15219: 15017: 14967: 14541: 14503: 14181: 14156: 14151: 14091: 13800: 13770: 13756: 13696: 13644: 13611: 13567: 13521: 13470: 13382: 13331: 13323: 13247: 13183: 12965: 12930: 12892: 12851: 12809: 12767: 12686: 12588: 12568: 11823: 11763: 11669: 11427: 11175: 11064: 10839: 10729: 9453:
Now, to perform our recursive call to the factorial function, we would simply call
3436:
The following definitions are necessary in order to be able to define β-reduction:
793: 642: 583: 502: 301: 281: 261: 241: 183: 94: 13922: 10744:. In fact computability can itself be defined via the lambda calculus: a function 10122:, while still allowing argument values to be substituted into the positions where 8930:
should be an abstraction, applying its parameter to a value to express recursion.
16376: 16271: 16236: 15912: 15902: 15839: 15794: 15756: 15658: 15578: 15385: 15312: 15285: 15273: 15179: 15093: 15067: 15022: 14990: 14791: 14593: 14536: 14486: 14451: 14409: 14136: 14053: 13968: 13952: 13941: 13929: 13899: 13327: 13050: 12660: 12633: 12602: 12516: 11925: 11597: 11549: 11483: 11450: 11372: 11342: 11253: 11115: 10921: 10741: 10716:
There is no algorithm that takes as input any two lambda expressions and outputs
10486: 8982:
here) must always be passed to itself within the function body, at a call point:
8810: 7185: 6834: 2560:
Parentheses may be used and might be needed to disambiguate terms. For example,
750:” to distinguish function-abstraction from class-abstraction, and then changing “ 595: 490: 13719:
Asperti, Andrea (16 Jan 2017). "About the efficient reduction of lambda terms".
13701: 13684: 12635:
Categorial Investigations: Logical and Linguistic Aspects of the Lambek Calculus
11742:
An introduction to λ-calculi and arithmetic with a decent selection of exercises
11051:. However, function pointers are not a sufficient condition for functions to be 6585:
The meaning of lambda expressions is defined by how expressions can be reduced.
6337:
When all variables are single-letter, the space in applications may be omitted:
2426:
A lambda term may refer to a variable that has not been bound, such as the term
16659: 16654: 16574: 16458: 16336: 16231: 16072: 15897: 15876: 15834: 15814: 15709: 15564: 15162: 15152: 15142: 15137: 15071: 14945: 14821: 14710: 14705: 14683: 14284: 14176: 13171: 12793: 11749: 11462: 11421: 11263: 10900: 10816: 10069:
is a lambda-term without abstraction, but possibly containing named constants (
9236: 7235: 7231: 7154: 7098: 7094: 4607: 3251:, no matter the input. As an example of a function operating on functions, the 657:
There is some uncertainty over the reason for Church's use of the Greek letter
619: 594:
implement lambda calculus. Lambda calculus is also a current research topic in
529: 403: 62: 13857: 13526: 13386: 13272: 11767: 8678:
As an example of the use of pairs, the shift-and-increment function that maps
8305:
is a function that returns a Boolean value. The most fundamental predicate is
7505:, which is often useful when analysing programs, is as an instruction 'repeat 16699: 16346: 16321: 16155: 15871: 15549: 15056: 14841: 14831: 14801: 14786: 14456: 14024: 13474: 12918: 12880: 12835: 12755: 11754: 11535: 11384: 11236: 11179: 11164: 10724:
depending on whether one expression reduces to the other. More precisely, no
10693:
Strategies with sharing reduce computations that are "the same" in parallel:
10674:
is in normal form according to this strategy, although it contains the redex
6814:
In programming languages with static scope, α-conversion can be used to make
789: 607: 66: 38: 30: 13648: 13615: 13029: 11752:(2008). "On Reduction Rules, Meaning-as-Use and Proof-Theoretic Semantics". 11745:. Notes for a course in the Mathematical Logic MSc at Manchester University. 508:
Variable names are not needed if using a universal lambda function, such as
16614: 16534: 16401: 16281: 16165: 16145: 15771: 15618: 15519: 15511: 15391: 15339: 15248: 15184: 15167: 15098: 14957: 14816: 14518: 14301: 13740: 12797: 11693: 11479: 11186: 10964: 10474: 10463: 7101:
they give the same result for all arguments. η-reduction converts between λ
1885:
programs and some are not. A valid lambda calculus expression is called a "
623: 509: 50: 13761: 13744: 13571: 11424:– A kind of constructive logical formula such that proofs are lambda terms 10989:
the "square" function can be expressed as a lambda expression as follows:
9215:
Given a lambda term with first argument representing recursive call (e.g.
8030:. With the predecessor function, subtraction is straightforward. Defining 586:. Lambda calculus has played an important role in the development of the 16529: 16503: 16386: 16150: 16077: 15881: 15761: 14940: 14930: 14877: 14561: 14481: 14466: 14346: 14291: 14223: 14146: 14121: 14081: 13961:, a graphical Java applet demonstrating alternative reduction strategies. 13865: 12556: 11827: 11646: 11228: 11205: 11144: 11040: 6509:) and is defined by recursion on the structure of the terms, as follows: 6030: 5736: 615: 579: 571: 10462:
languages. Typed lambda calculi play an important role in the design of
16679: 16326: 16092: 16047: 16042: 14811: 14666: 14637: 14443: 14171: 13915: 13514:
13th International Conference on Interactive Theorem Proving (ITP 2022)
13469:. Lecture Notes in Computer Science. Vol. 2566. pp. 420–435. 13335: 12942: 12904: 12863: 12821: 12779: 12580: 12466:
Ariola and Blom employ 1) axioms for a representational calculus using
11171: 11060: 7195: 3571: 3495: 777: 575: 11561: 10835:
for other approaches to defining computability and their equivalence.
8632:
A linked list can be defined as either NIL for the empty list, or the
16478: 16296: 16221: 16200: 16130: 16082: 16062: 15963: 15866: 14919: 14836: 14796: 14760: 14696: 14508: 14498: 14471: 14234: 13725: 13434: 12368:
free variables in lambda Notation and its Calculus are comparable to
11831: 11473: 11056: 11044: 10604:{\displaystyle (\;\lambda x.y\;\;(\lambda z.(zz)\;\lambda z.(zz))\;)} 8934: 8900: 8399:, it is straightforward to build a predicate for numerical equality. 7015:α-equivalence. Substitution is defined uniquely up to α-equivalence. 57:. Untyped lambda calculus, the topic of this article, is a universal 13986: 12934: 12896: 12855: 12813: 12771: 12572: 7581:, where '(mf)x' means the function 'f' is applied 'm' times on 'x': 16391: 16180: 15948: 15746: 15194: 14899: 14493: 13639: 11512: 11435:– A demonstration that some form of lambda calculus is inconsistent 11239:
are extensions of lambda calculus that are not in the lambda cube:
11218: 10641:
Weak reduction strategies do not reduce under lambda abstractions:
8868:; this means a recursive function definition cannot be used as the 7422:, and returns another single-argument function. The Church numeral 2512:
has not been defined and is considered an unknown. The abstraction
1896:
that can be applied to build all syntactically valid lambda terms:
1870: 1309: 13946: 13825: 13322:. Lecture Notes in Computer Science. Vol. 8560. p. 196. 13149: 11509:– A formal computing machine that is equivalent to lambda calculus 11453:– An abstract machine to interpret call-by-name in lambda calculus 11118:
have been developed for describing communication and concurrency.
10347:, but pass the argument on to only one subterm of an application ( 6837:
notation, any two α-equivalent terms are syntactically identical.
4917:{\displaystyle ((\lambda x.y)x)=((\lambda x.y))(x)=(\lambda x.y)y} 15544: 14336: 13860:, a short (12 minutes) Computerphile video on the Lambda Calculus 11924:
by Peter Kelly, Paul Coddington, and Andrew Wendelborn; mentions
11723:
An Introduction to Functional Programming Through Lambda Calculus
11357: 11080: 8880:
construction would allow writing recursive function definitions.
7562:
We can define a successor function, which takes a Church numeral
6611:
We also speak of the resulting equivalences: two expressions are
1521:
whereas evaluation of the curried version requires one more step
13993: 13745:"A Correspondence between ALGOL 60 and Church's Lambda-notation" 13548:
Frandsen, Gudmund Skovbjerg; Sturtivant, Carl (26 August 1991).
13368:"Call-by-Value Lambda Calculus as a Model of Computation in Coq" 13109: 11564:. The Bulletin of Symbolic Logic, Volume 3, Number 2, June 1997. 11039:
and many other imperative languages have long supported passing
11024:
creates an anonymous function, given a list of parameter names,
8972:
In the lambda expression which is to represent this function, a
5307:, and the meaning of the function is preserved by substitution. 4365: ; substitution distributes to both sides of an application 402:, renaming the bound variables in the expression. Used to avoid 13520:. Schloss Dagstuhl – Leibniz-Zentrum für Informatik: 7:1–7:19. 12144: 11562:
The Impact of the Lambda Calculus in Logic and Computer Science
11032:. Anonymous functions are sometimes called lambda expressions. 5075:. This erroneous substitution would turn the constant function 1005: 658: 13226:(29 Dec 2010) Haskell-cafe: What's the motivation for η rules? 11698:
A Correspondence Between ALGOL 60 and Church's Lambda-Notation
8230:
We are now able to compute some logic functions, for example:
7330:
and so on. Or using the alternative syntax presented above in
16256: 15088: 14434: 14279: 13891: 13815:
Written 1969, widely circulated as an unpublished manuscript.
12883:(1936). "An unsolvable problem of elementary number theory". 12258: 10942:
An unreasonable model does not necessarily mean inefficient.
10862:
is applied to its own Gödel number, a contradiction results.
8896:
SKI combinator calculus § Self-application and recursion
7012: 6705: 993: 914:{\displaystyle \operatorname {square\_sum} (x,y)=x^{2}+y^{2}} 156:
is a function definition, taking as input the bound variable
11185:
with the required property could be found, thus providing a
10958: 6565:
An expression that contains no free variables is said to be
5315:
The β-reduction rule states that an application of the form
1180:
function, that in turn accepts a single input. For example,
570:
Lambda calculus has applications in many different areas in
13414:
Types and Programming Languages, p. 273, Benjamin C. Pierce
12800:(July 1935). "The Inconsistency of Certain Formal Logics". 12758:(1932). "A set of postulates for the foundation of logic". 12541: 10948: 10489:, e.g. the simply typed lambda calculus is the language of 8402:
The availability of predicates and the above definition of
7097:, which in this context is that two functions are the same 7033: 3331:
A basic form of equivalence, definable on lambda terms, is
13934: 13507:"The Zoo of Lambda-Calculus Reduction Strategies, and Coq" 13313:"Preciseness of Subtyping on Intersection and Union Types" 13311:
Dezani-Ciancaglini, Mariangiola; Ghilezan, Silvia (2014).
13310: 11786:
An Introduction to Lambda Calculi for Computer Scientists,
11519:
functional programming language based on combinatory logic
10846:
for lambda expressions, he constructs a lambda expression
8817:, to permit writing the above in the more intuitive order 497:
of the reduction steps eventually terminates, then by the
12370:
linear algebra and mathematical concepts of the same name
11704:, vol. 8, no. 2 (1965), pages 89–101. Available from the 9468:
is the number we are calculating the factorial of. Given
7127:η-reduction can be seen to be the same as the concept of 7090: 7066:β-reduction can be seen to be the same as the concept of 65:(and vice versa). It was introduced by the mathematician 13550:"What is an efficient implementation of the λ-calculus?" 11259:
These formal systems are variations of lambda calculus:
6650:. The expression to which a redex reduces is called its 16022: 13504: 12921:(1940). "A Formulation of the Simple Theory of Types". 8786:(another lambda-term, the "main program"), one can say 7533:
times, starting from an empty list. The lambda term is
7234:
in lambda calculus, but by far the most common are the
5300:{\displaystyle (\lambda z.y)=\lambda z.(y)=\lambda z.x} 5068:{\displaystyle (\lambda x.y)=\lambda x.(y)=\lambda x.x} 4768:{\displaystyle (\lambda x.x)=\lambda x.(x)=\lambda x.x} 3657:
For example, the lambda term representing the identity
13916:
Alligator Eggs: A Puzzle Game Based on Lambda Calculus
12491:
Some parts of this article are based on material from
11215:– Lambda calculus with typed variables (and functions) 11139:, of functions on itself. However, no nontrivial such 10061:
Combinatory logic § Completeness of the S-K basis
9242:
In fact, there are many possible definitions for this
9235:
is re-created inside itself, at call-point, achieving
3102: 1826: 1741: 1635: 1530: 1500: 1456: 1376: 1324: 1133: 1014: 414: 331: 304: 284: 264: 244: 208: 186: 123: 97: 13786:"A type-theoretical alternative to ISWIM, CUCH, OWHY" 12559:(December 1937). "Computability and λ-Definability". 12511: 12509: 12507: 12419: 12399: 12339: 12304: 12267: 12228: 12162: 12129: 11963: 11277:– A notation for mathematical logic without variables 11270:
These formal systems are related to lambda calculus:
10617: 10529: 10417: 10355:
to the "function" subterm), thus saving a subsequent
5810: 5745: 5705: 5640: 5611: 5546: 5526: 5491: 5453: 5394: 5359: 5321: 5212: 5192: 5186:
the abstraction can be renamed with a fresh variable
5142: 5110: 5081: 4980: 4957: 4933: 4781: 4680: 4656: 4636: 4616: 4592: 4572: 4552: 4526: 4440: 4373: 4282: 4260: 4239: 4219: 4199: 4179: 4159: 4133: 4092: 4071: 4051: 4031: 4011: 3970: 3943: 3923: 3903: 3868: 3848: 3828: 3808: 3788: 3768: 3740: 3720: 3692: 3663: 3639: 3619: 3599: 3580: 3553: 3533: 3504: 3478: 3458: 3419: 3399: 3370: 3341: 3313:{\displaystyle \lambda f.\lambda g.\lambda x.(f(gx))} 3261: 3237: 3211: 3179: 3153: 3120: 3076: 3053: 3033: 2983: 2963: 2943: 2923: 2903: 2868: 2830: 2810: 2781: 2742: 2722: 2702: 2653: 2622: 2569: 2518: 2473: 2432: 2400: 2386:, that is, it represents the act of calling function 2364: 2344: 2292: 2272: 2235: 2184: 2164: 2116: 2075: 2030: 1994: 1971: 1921: 1873:
is used to implement functions of several variables.
1804: 1784: 1719: 1699: 1253: 1189: 1101: 1057: 937: 834: 756: 733: 704: 671: 162: 12963: 11309: 8742: 6724:. Terms that differ only by α-conversion are called 5797:{\displaystyle \Omega =(\lambda x.xx)(\lambda x.xx)} 2769: 12515: 11806:Sørensen, Morten Heine and Urzyczyn, Paweł (2006), 11252:– An extension of the lambda calculus for treating 8862:to be outside the scope of the abstraction binding 7018: 2286:is superfluous when using abstraction. The syntax 392:{\textstyle (\lambda x.M)\rightarrow (\lambda y.M)} 13547: 12504: 12425: 12405: 12351: 12325: 12282: 12249: 12199: 12135: 12071: 11465:– An expression closely related to an abstraction. 11147:constraints because the set of all functions from 10623: 10603: 10423: 8455:which can be verified by showing inductively that 7723:are β-equivalent lambda expressions. Since adding 7200: 7153:For the untyped lambda calculus, β-reduction as a 6478:in the expression is bound by the second lambda: λ 6017: 5796: 5720: 5691: 5626: 5597: 5532: 5512: 5477: 5439: 5380: 5345: 5299: 5198: 5178: 5125: 5096: 5067: 4963: 4939: 4916: 4767: 4662: 4642: 4622: 4598: 4578: 4558: 4538: 4512: 4424: 4357: 4269: 4245: 4225: 4205: 4185: 4165: 4145: 4119: 4077: 4057: 4037: 4017: 3997: 3949: 3929: 3909: 3889: 3854: 3834: 3814: 3794: 3774: 3746: 3726: 3707: 3678: 3645: 3625: 3605: 3586: 3559: 3539: 3519: 3484: 3464: 3425: 3405: 3385: 3356: 3312: 3243: 3223: 3194: 3165: 3135: 3091: 3059: 3039: 3019: 2969: 2949: 2929: 2909: 2889: 2854: 2816: 2796: 2748: 2728: 2708: 2689: 2637: 2608: 2545: 2500: 2459: 2415: 2370: 2350: 2313: 2278: 2254: 2221: 2170: 2150: 2090: 2055: 2003: 1980: 1942: 1835: 1810: 1790: 1770: 1733:in the inner expression. This is like β-reduction. 1725: 1705: 1685: 1620: 1509: 1485: 1441: 1359: 1297: 1233: 1168: 1113: 1081: 1040: 981: 913: 762: 742: 719: 686: 610:in the 1930s as part of an investigation into the 474: 391: 310: 290: 270: 250: 226: 192: 168: 144: 115:is a character or string representing a parameter. 103: 13628: 11609:An unsolvable problem of elementary number theory 11532:Structure and Interpretation of Computer Programs 11366:– The formal correspondence between programs and 6313:Applications are assumed to be left associative: 3757: 1604: 1533: 1367:function to the arguments (5, 2), yields at once 16697: 16489:Segmented discourse representation theory (SDRT) 13689:Electronic Notes in Theoretical Computer Science 11645: 11591:History of Lambda-calculus and Combinatory Logic 9974:systems that can express any lambda term - see 8636:of an element and a smaller list. The predicate 7956:can be validated by showing inductively that if 7225: 606:Lambda calculus was introduced by mathematician 73:. In 1936, Church found a formulation which was 13949:a simple yet powerful pure calculus interpreter 13119:so we cannot use this juxtaposition convention. 13083: 13081: 11381:– notation using postfix modification functions 8321:if its argument were any other Church numeral: 7194:The basic lambda calculus may be used to model 6638:is a β-redex in expressing the substitution of 6073:the abstraction symbols λ (lambda) and . (dot); 3107:In lambda calculus, functions are taken to be ' 1298:{\displaystyle x\mapsto (y\mapsto x^{2}+y^{2})} 796:. Why did you choose lambda for your operator? 515: 13366:Forster, Yannick; Smolka, Gert (August 2019). 13236: 12957: 12838:(December 1942). "Review of Haskell B. Curry, 12716: 12200:{\displaystyle e::=x\mid \lambda x.e\mid e\,e} 11889:A Tutorial Introduction to the Lambda Calculus 11086: 11047:to other subprograms through the mechanism of 10831:meaning equivalence with β-reduction. See the 10381:combinator does only the latter, yielding the 8675:obviates the need for an explicit NULL test). 7230:There are several possible ways to define the 7142: 6569:. Closed lambda expressions are also known as 3067:. Both examples 1 and 2 would evaluate to the 1854:The lambda calculus consists of a language of 475:{\textstyle ((\lambda x.M)\ N)\rightarrow (M)} 69:in the 1930s as part of his research into the 16008: 14250: 14009: 13678: 13676: 13365: 13200: 13056:The Lambda Calculus: Its Syntax and Semantics 12875: 12873: 12742:Basic Category Theory for Computer Scientists 12659:Bunt, Harry; Muskens, Reinhard, eds. (2008). 12095:Barendregt, Barendsen (2000) call this form 11714:An Introduction to Lambda Calculus and Scheme 11684:A theory of positive integers in formal logic 11589:Cardone, Felice and Hindley, J. Roger, 2006. 11476:– Transformation of formulæ in formal systems 11401:– Rules for the evaluation of expressions in 11221:– A typed lambda calculus with type-variables 9990:, the smallest term that has no normal form. 8883: 7499:One way of thinking about the Church numeral 7168:However, it can be shown that β-reduction is 6976: 4948: 3613:is the union of the set of free variables of 1588: 1540: 13953:Lambda Calculus links on Lambda-the-Ultimate 13866:Step by Step Introduction to Lambda Calculus 13237:Felleisen, Matthias; Flatt, Matthew (2006), 13078: 12792: 12720:Introduction to Lambda Calculus using Racket 11441:– A semi-fictional organization of LISP and 11199: 11099:, even in parallel. This means that various 10469:Typed lambda calculi are closely related to 10263:can reduce by having the initial combinator 9975: 9758:Certain terms have commonly accepted names: 9725:4 × (3 × (2 × (1 × (1, if 0 = 0; else 0 × (( 8509:A pair (2-tuple) can be defined in terms of 7895:is considerably more difficult. The formula 7766:Similarly, multiplication can be defined as 6607:: which captures a notion of extensionality. 4566:does not appear among the free variables of 2158:is an abstraction representing the function 1442:{\textstyle ((x,y)\mapsto x^{2}+y^{2})(5,2)} 1124:where the input is simply mapped to itself. 16:Mathematical-logic system based on functions 13685:"(In)Efficiency and Reasonable Cost Models" 13129: 13127: 12658: 12605:(8 February 2006). Zalta, Edward N. (ed.). 11865:A Short Introduction to the Lambda Calculus 11459:– Formal definition of the lambda calculus. 11375:– notation disambiguating alpha conversions 11266:– A first-order analogue of lambda calculus 8541:returns the first element of the pair, and 7149:Normalization property (abstract rewriting) 6417: 6389:A sequence of abstractions is contracted: λ 4513:{\displaystyle (\lambda y.t)=\lambda y.(t)} 16015: 16001: 14442: 14257: 14243: 14016: 14002: 13714: 13712: 13673: 13170: 13049: 12870: 12840:The Inconsistency of Certain Formal Logics 12695:. Cambridge University Press. p. 57. 12393:The union of the set of free variables of 12380:The set of free variables of M, but with { 11822:, including more recent developments like 11799:Monographs/textbooks for graduate students 11748: 11720: 11530:Abelson, Harold & Gerald Jay Sussman. 10597: 10572: 10547: 10546: 10533: 10054: 6828:α-renaming to make name resolution trivial 6818:simpler by ensuring that no variable name 2609:{\displaystyle \lambda x.((\lambda x.x)x)} 2467:(which represents the function definition 13760: 13724: 13700: 13682: 13638: 13561: 13525: 13460:"Demonstrating Lambda Calculus Reduction" 13218: 13201:Turbak, Franklyn; Gifford, David (2008), 13148: 13110:"The Basic Grammar of Lambda Expressions" 12193: 12120: 12118: 11957:These rules produce expressions such as: 11673: 11410:– The theory of substitution, as used in 10959:Lambda calculus and programming languages 10503:Reduction strategy § Lambda calculus 10036: 8755:, effectively using lambda calculus as a 8023: 7206: 4425:{\displaystyle (\lambda x.t)=\lambda x.t} 3020:{\displaystyle (\lambda x.(\lambda x.x))} 2690:{\displaystyle (\lambda x.(\lambda x.x))} 2378:represents the application of a function 1360:{\textstyle \operatorname {square\_sum} } 1169:{\textstyle \operatorname {square\_sum} } 648: 80:Lambda calculus consists of constructing 13240:Programming Languages and Lambda Calculi 13203:Design concepts in programming languages 13133: 13124: 12685: 12631: 12150: 11940:graph reduction for lambda expressions). 11808:Lectures on the Curry–Howard isomorphism 11717:. A gentle introduction for programmers. 11192:This work also formed the basis for the 10392: 6601:: applying functions to their arguments; 6033:, strings, or other non-number objects. 4927:The freshness condition (requiring that 3686:has no free variables, but the function 1234:{\displaystyle (x,y)\mapsto x^{2}+y^{2}} 1082:{\displaystyle \operatorname {id} (x)=x} 982:{\displaystyle (x,y)\mapsto x^{2}+y^{2}} 13718: 13709: 13457: 13263: 13261: 13008:The Stanford Encyclopedia of Philosophy 12611:The Stanford Encyclopedia of Philosophy 12601: 11625:. Princeton: Princeton University Press 10496: 9682:4 × (3 × (2 × (1, if 1 = 0; else 1 × (( 8092: 1686:{\textstyle =(y\mapsto 5^{2}+y^{2})(2)} 807: 564: 16698: 14264: 13739: 13423: 13002:Alama, Jesse. Zalta, Edward N. (ed.). 12917: 12879: 12834: 12754: 12555: 12460: 12115: 12091: 12089: 12087: 12085: 11837: 11618: 11492:– A theorem about sets of lambda terms 11283:– A computational system based on the 10974: 10442:Typed lambda calculi are foundational 9246:operator, the simplest of them being: 8313:if its argument is the Church numeral 7657:, addition can be defined as follows: 2645:and is therefore an abstraction, while 1849: 1092:can be rewritten in anonymous form as 614:. The original system was shown to be 16444:Discourse representation theory (DRT) 15996: 14238: 14203:University of California, Los Angeles 13997: 13783: 13683:Accattoli, Beniamino (October 2018). 13594: 13040:at the University of Birmingham, UK.) 12717:Chacón Sartori, Camilo (2023-12-05). 11951: 7741:times, an alternative definition is: 7416:—it takes a single-argument function 7179: 6689:is also an η-redex, with a reduct of 6156:and instances of rule 3 are known as 5692:{\displaystyle (\lambda x.y)s\to y=y} 5598:{\displaystyle (\lambda x.x)s\to x=s} 4650:is "fresh" for the substitution term 557:typed lambda calculi can express less 13258: 13137:Lecture Notes on the Lambda Calculus 13089:"Example for Rules of Associativity" 12457:can be pronounced "let f be N in M". 11901:Lecture Notes on the Lambda Calculus 10854:Gödel's first incompleteness theorem 10304:throws the argument away, just like 7873:The predecessor function defined by 7428:is a function that takes a function 6588:There are three kinds of reduction: 6169:This set of rules may be written in 6052:Lambda expressions are composed of: 6036: 3326: 16357:Quantificational variability effect 16024:Formal semantics (natural language) 13980:Internet Encyclopedia of Philosophy 13900:Some executable λ-calculus examples 12971:Mathematical Methods in Linguistics 12211:Simply typed lambda calculus#Syntax 12082: 11921:Lambda Calculus as a Workflow Model 11341:– A setting for lambda calculus in 11335:in the style of the lambda calculus 10439:a special case with only one type. 10245:In either case, a term of the form 10073:), then there exists a lambda-term 7238:, which can be defined as follows: 7017:See Capture-avoiding substitutions 6354:The body of an abstraction extends 6296:Outermost parentheses are dropped: 5634:really is the identity. Similarly, 5440:{\displaystyle (\lambda x.t)s\to t} 3231:, the function that always returns 3103:Functions that operate on functions 2765:is a placeholder in both examples. 2151:{\displaystyle \lambda x.(x^{2}+2)} 176:(between the λ and the punctum/dot 112: 13: 13830:Mathematical and Computer Sciences 13320:Rewriting and Typed Lambda Calculi 13188:10.1111/j.1746-8361.1988.tb00919.x 12737: 12723:(Technical report). Archived from 11739:Schalk, A. and Simmons, H. (2005) 11721:Michaelson, Greg (10 April 2013). 11524: 10852:that closely follows the proof of 10481:and they can be considered as the 9639:4 × (3 × (1, if 2 = 0; else 2 × (( 8762: 6849:, is the process of replacing all 6458:. For example, in the expression λ 5746: 2099: 1892:The following three rules give an 1353: 1350: 1347: 1344: 1341: 1338: 1335: 1332: 1329: 1326: 1162: 1159: 1156: 1153: 1150: 1147: 1144: 1141: 1138: 1135: 863: 860: 857: 854: 851: 848: 845: 842: 839: 836: 322:The reduction operations include: 14: 16742: 14219:Alonzo Church (college president) 14023: 13850: 13030:Looking Backward; Looking Forward 13001: 12692:Concepts in Programming Languages 12413:and the set of free variables of 11131:isomorphic to the function space 11110:. One can add constructs such as 10365:in one subterm. In comparison to 9753: 8743:Additional programming techniques 7837:is the same as repeating the add 7575:by adding another application of 7093:reduction) expresses the idea of 6454:. All other variables are called 6152:Instances of rule 2 are known as 3961:manner. This is defined so that: 3633:and the set of free variables of 3439: 528:that can be used to simulate any 399: 81: 61:that can be used to simulate any 15976: 13965:Implementing the Lambda calculus 13604:Journal of Logic and Computation 13267:Zena M. Ariola and Stefan Blom, 12519:; Barendsen, Erik (March 2000), 12475: 12468:well-formed cyclic lambda graphs 11653:The Calculi of Lambda-Conversion 11622:The Calculi of Lambda-Conversion 11602:Handbook of the History of Logic 11486:designed for the lambda calculus 11411: 11312: 10711: 10448:functional programming languages 8747:There is a considerable body of 7735:can be accomplished by adding 1 7024: 6811:, which is not at all the same. 6446:is getting bound by prepending λ 3527:is the set of free variables of 2756:and is therefore an application. 2056:{\displaystyle \lambda x.x^{2}.} 1818:. Again, similar to β-reduction. 694:” used for class-abstraction by 592:Functional programming languages 482: 153: 13818: 13777: 13733: 13622: 13588: 13541: 13498: 13451: 13430:Types and Programming Languages 13417: 13408: 13359: 13304: 13284: 13278: 13230: 13194: 13164: 13102: 13043: 13022: 12995: 12911: 12885:American Journal of Mathematics 12828: 12786: 12748: 12731: 12710: 12522:Introduction to Lambda Calculus 12435: 12387: 12374: 12362: 12292: 12217: 12106: 11840:Types and Programming Languages 11688:American Journal of Mathematics 11675:10.1090/s0002-9904-1944-08090-7 11613:American Journal of Mathematics 11554:Introduction to Lambda Calculus 11227:– A typed lambda calculus with 8782:(some explicit lambda-term) in 7509:times'. For example, using the 6840: 6696: 6573:and are equivalent to terms in 6080:The set of lambda expressions, 2546:{\displaystyle \lambda x.(x+y)} 2460:{\displaystyle \lambda x.(x+y)} 1876: 770:” to “λ” for ease of printing. 588:theory of programming languages 16439:Combinatory categorial grammar 13375:Journal of Automated Reasoning 12679: 12652: 12625: 12595: 12549: 12531: 12343: 12320: 12305: 12244: 12229: 12130: 12066: 12063: 12051: 12048: 12045: 12024: 12018: 11997: 11985: 11964: 11600:. In Gabbay and Woods (eds.), 11573:Handbook of Mathematical Logic 11439:Knights of the Lambda Calculus 11114:to the lambda calculus. Other 10598: 10594: 10591: 10582: 10569: 10560: 10548: 10530: 10523:exists. For example, the term 10351:to the "argument" subterm and 9472:= 4, for example, this gives: 8844:A notable restriction of this 8757:low-level programming language 8753:programming language semantics 7525:by repeating 'prepend another 7081: 6442:, as a hint that the variable 6012: 5994: 5991: 5973: 5967: 5964: 5940: 5934: 5931: 5928: 5904: 5898: 5892: 5868: 5865: 5856: 5853: 5850: 5832: 5829: 5811: 5791: 5773: 5770: 5752: 5680: 5668: 5662: 5656: 5641: 5586: 5574: 5568: 5562: 5547: 5507: 5495: 5478:{\displaystyle (\lambda x.t)s} 5469: 5454: 5434: 5422: 5416: 5410: 5395: 5375: 5363: 5346:{\displaystyle (\lambda x.t)s} 5337: 5322: 5310: 5279: 5276: 5264: 5258: 5243: 5231: 5228: 5213: 5173: 5161: 5158: 5143: 5047: 5044: 5032: 5026: 5011: 4999: 4996: 4981: 4908: 4893: 4887: 4884: 4872: 4866: 4863: 4860: 4848: 4845: 4830: 4827: 4821: 4809: 4806: 4800: 4785: 4782: 4747: 4744: 4732: 4726: 4711: 4699: 4696: 4681: 4507: 4504: 4492: 4486: 4471: 4459: 4456: 4441: 4404: 4392: 4389: 4374: 4352: 4349: 4337: 4331: 4328: 4325: 4313: 4307: 4301: 4289: 4286: 4261: 4108: 4096: 3986: 3974: 3884: 3872: 3758:Capture-avoiding substitutions 3307: 3304: 3295: 3289: 3215: 3157: 3014: 3011: 2996: 2984: 2884: 2869: 2855:{\displaystyle (\lambda x.x)x} 2846: 2831: 2684: 2681: 2666: 2654: 2603: 2597: 2582: 2579: 2540: 2528: 2508:). In this term, the variable 2483: 2477: 2454: 2442: 2410: 2404: 2308: 2293: 2194: 2188: 2145: 2126: 1998: 1972: 1937: 1922: 1904:is itself a valid lambda term. 1846:to arrive at the same result. 1680: 1674: 1671: 1645: 1639: 1615: 1609: 1599: 1593: 1583: 1557: 1551: 1548: 1436: 1424: 1421: 1395: 1392: 1380: 1377: 1292: 1266: 1260: 1257: 1205: 1202: 1190: 1105: 1070: 1064: 953: 950: 938: 882: 870: 711: 678: 469: 466: 454: 448: 445: 442: 433: 418: 415: 386: 383: 377: 362: 359: 356: 353: 347: 332: 221: 209: 139: 124: 85: 1: 16217:Antecedent-contained deletion 15937:History of mathematical logic 12844:The Journal of Symbolic Logic 12561:The Journal of Symbolic Logic 12485: 12326:{\displaystyle (\lambda x.t)} 12250:{\displaystyle (\lambda x.t)} 11877:A timeline of lambda calculus 11569:The Type Free Lambda Calculus 11354:applicable to lambda calculus 11329:Applicative computing systems 11155:has greater cardinality than 10865: 10433:Kinds of typed lambda calculi 10411:that uses the lambda-symbol ( 10359:if there is no occurrence of 10112:) removes all occurrences of 10006:, and can also be defined as 9596:4 × (1, if 3 = 0; else 3 × (( 7476:(considered as an operator); 7332: 7226:Arithmetic in lambda calculus 6047: 5179:{\displaystyle (\lambda x.y)} 3114:For example, the lambda term 2890:{\displaystyle (\lambda x.x)} 2314:{\displaystyle (\lambda x.t)} 2222:{\displaystyle f(x)=x^{2}+2,} 2021: 1943:{\displaystyle (\lambda x.t)} 812: 524:, that is, it is a universal 235: 77:, and documented it in 1940. 16731:Theoretical computer science 15862:Primitive recursive function 14044:Simply typed lambda calculus 13826:"Greg Michaelson's Homepage" 13805:10.1016/0304-3975(93)90095-B 13793:Theoretical Computer Science 13328:10.1007/978-3-319-08918-8_14 13273:(1997) Cyclic lambda calculi 13246:, p. 26, archived from 11567:Barendregt, Hendrik Pieter, 11560:Barendregt, Hendrik Pieter, 11348:Categorical abstract machine 11204:These extensions are in the 11121: 10760:such that for every pair of 10458:and, more indirectly, typed 10039:are commonly abbreviated as 9302:  is a fixed-point of 7434:as argument and returns the 6853:occurrences of the variable 6580: 6323:may be written instead of (( 3862:are variables. The notation 3734:has a single free variable, 2011:is a lambda term (called an 1950:is a lambda term (called an 1048:"). Similarly, the function 636:simply typed lambda calculus 561:simply typed lambda calculus 516:Explanation and applications 74: 7: 13908:The Lambda Calculus and A++ 13878:Encyclopedia of Mathematics 13702:10.1016/j.entcs.2018.10.003 13287:"Lambda Calculus and Types" 12213:for untyped lambda calculus 11305: 11087:Parallelism and concurrency 10491:Cartesian closed categories 10279:, just like β-reduction of 8022:are given below, one using 8018:. Two other definitions of 7143:Normal forms and confluence 6595:: changing bound variables; 6287: 5721:{\displaystyle \lambda x.y} 5627:{\displaystyle \lambda x.x} 5126:{\displaystyle \lambda x.x} 5097:{\displaystyle \lambda x.y} 3708:{\displaystyle \lambda x.y} 3679:{\displaystyle \lambda x.x} 3520:{\displaystyle \lambda x.t} 3386:{\displaystyle \lambda y.y} 3357:{\displaystyle \lambda x.x} 3195:{\displaystyle \lambda x.y} 3136:{\displaystyle \lambda x.x} 3092:{\displaystyle \lambda x.x} 3027:being applied to the input 2957:, is M applied to N, where 2797:{\displaystyle \lambda x.B} 2638:{\displaystyle \lambda x.B} 2091:{\displaystyle \lambda x.t} 10: 16747: 16098:Syntax–semantics interface 14926:Schröder–Bernstein theorem 14653:Monadic predicate calculus 14312:Foundations of mathematics 13973:Shane Steinert-Threlkeld, 13467:The Essence of Computation 13205:, MIT press, p. 251, 13051:Barendregt, Hendrik Pieter 13038:extract of a May 2016 talk 12632:Moortgat, Michael (1988). 12359:written in anonymous form. 12352:{\displaystyle x\mapsto t} 11550:Barendregt, Hendrik Pieter 11457:Lambda calculus definition 11196:of programming languages. 11178:were considered, a set or 10978: 10500: 10446:and are the base of typed 10396: 10324:has no free occurrence in 10132:. The conversion function 10058: 9958:is the identity function. 9132: to hold, so  9043: to hold, so  8893: 8887: 8884:Recursion and fixed points 8027: 7212: 7183: 7146: 6999:, because the substituted 6163: 6043:Lambda calculus definition 6040: 5699:, which demonstrates that 3897:indicates substitution of 3224:{\displaystyle x\mapsto y} 3166:{\displaystyle x\mapsto x} 2102:that takes a single input 1114:{\displaystyle x\mapsto x} 720:{\displaystyle {\hat {x}}} 687:{\displaystyle {\hat {x}}} 612:foundations of mathematics 601: 145:{\textstyle (\lambda x.M)} 71:foundations of mathematics 16632: 16590:Question under discussion 16540:Conversational scoreboard 16517: 16421: 16414: 16317:Intersective modification 16302:Homogeneity (linguistics) 16209: 16118: 16111: 16030: 15972: 15959:Philosophy of mathematics 15908:Automated theorem proving 15890: 15785: 15617: 15510: 15362: 15079: 15055: 15033:Von Neumann–Bernays–Gödel 14978: 14872: 14776: 14674: 14665: 14592: 14527: 14433: 14355: 14272: 14211: 14190: 14074: 14031: 13749:Communications of the ACM 13527:10.4230/LIPIcs.ITP.2022.7 13387:10.1007/s10817-018-9484-2 12923:Journal of Symbolic Logic 12802:The Annals of Mathematics 11838:Pierce, Benjamin (2002), 11768:10.1007/s11225-008-9150-5 11702:Communications of the ACM 11339:Cartesian closed category 11225:Calculus of constructions 11200:Variations and extensions 11189:for the lambda calculus. 10087:) which is equivalent to 9734:4 × (3 × (2 × (1 × (1)))) 8519:Church encoding for pairs 5605:. This demonstrates that 5520:. For example, for every 5447:is used to indicate that 4358:{\displaystyle s)=(t)(s)} 1771:{\textstyle =5^{2}+2^{2}} 1486:{\textstyle =5^{2}+2^{2}} 180:) and returning the body 16650:Distributional semantics 13832:. Riccarton, Edinburgh: 13475:10.1007/3-540-36377-7_19 13172:de Queiroz, Ruy J. G. B. 13134:Selinger, Peter (2008), 12333:represents the function 12257:is sometimes written in 12136:{\displaystyle \mapsto } 11944: 11936:property, which enables 11507:Universal Turing machine 11364:Curry–Howard isomorphism 10991: 10872:computational complexity 10736:means computable by any 10479:Curry–Howard isomorphism 10424:{\displaystyle \lambda } 10002:is standard and defined 9553:1, if 4 = 0; else 4 × (( 9293:In the lambda calculus, 8809:Authors often introduce 8504: 7137:Curry–Howard isomorphism 7120:does not appear free in 7076:Curry–Howard isomorphism 6501:of a lambda expression, 6470:is a bound variable and 6418:Free and bound variables 6356:as far right as possible 6283: :== v1 | v2 | ... 6175: 5728:is a constant function. 2862:, an anonymous function 2501:{\displaystyle f(x)=x+y} 1041:{\textstyle x^{2}+y^{2}} 16645:Computational semantics 16382:Subsective modification 16186:Propositional attitudes 15609:Self-verifying theories 15430:Tarski's axiomatization 14381:Tarski's undefinability 14376:incompleteness theorems 13649:10.1145/2603088.2603105 13458:Sestoft, Peter (2002). 11913:Graphic lambda calculus 11725:. Courier Corporation. 11619:Church, Alonzo (1941). 11281:SKI combinator calculus 11067:, and more recently in 10437:untyped lambda calculus 10387:SKI combinator calculus 10300:returns that argument. 10055:Abstraction elimination 9691:4 × (3 × (2 × (1 × (G ( 8945:recursively defined by 8644:. (Alternatively, with 8525:encapsulates the pair ( 7885:for a positive integer 7458:times. This is denoted 7190:Mogensen–Scott encoding 6822:a name in a containing 4539:{\displaystyle x\neq y} 4146:{\displaystyle x\neq y} 2255:{\displaystyle x^{2}+2} 1965:are lambda terms, then 785:Dear Professor Church, 743:{\displaystyle \land x} 543:Lambda calculus may be 16675:Philosophy of language 16312:Inalienable possession 16292:Free choice inferences 16287:Faultless disagreement 16058:Generalized quantifier 15983:Mathematics portal 15594:Proof of impossibility 15242:propositional variable 14552:Propositional calculus 13947:LCI Lambda Interpreter 13834:Heriot-Watt University 13010:(Summer 2013 ed.) 12968:; Wall, R. E. (1990). 12638:. Foris Publications. 12613:(Summer 2013 ed.) 12427: 12407: 12353: 12327: 12284: 12251: 12201: 12137: 12073: 11750:de Queiroz, Ruy J.G.B. 11469:Minimalism (computing) 11417:Functional programming 11393:denotational semantics 11360:, programming language 11297: 11291: 11285: 11244:Binary lambda calculus 11194:denotational semantics 10969:procedural programming 10955:on pure lambda terms. 10625: 10605: 10460:imperative programming 10425: 10003: 9996:is another such term. 9700:4 × (3 × (2 × (1 × ((λ 9190:FIX G = G (FIX G) = (λ 8890:Fixed-point combinator 8767:In lambda calculus, a 7521:elements all equal to 7412:A Church numeral is a 6845:Substitution, written 6164:§ reducible expression 6019: 5798: 5722: 5693: 5628: 5599: 5534: 5514: 5479: 5441: 5382: 5347: 5301: 5200: 5180: 5127: 5098: 5069: 4965: 4941: 4918: 4769: 4664: 4644: 4624: 4600: 4580: 4560: 4540: 4514: 4426: 4359: 4271: 4247: 4227: 4207: 4187: 4167: 4147: 4121: 4079: 4059: 4039: 4019: 3999: 3951: 3931: 3911: 3891: 3856: 3836: 3822:are lambda terms, and 3816: 3796: 3776: 3748: 3728: 3709: 3680: 3647: 3627: 3607: 3588: 3561: 3541: 3521: 3486: 3466: 3452:The free variables of 3427: 3407: 3387: 3358: 3314: 3245: 3225: 3196: 3167: 3137: 3093: 3061: 3041: 3021: 2971: 2951: 2931: 2911: 2891: 2856: 2818: 2798: 2750: 2730: 2710: 2691: 2639: 2610: 2547: 2502: 2461: 2417: 2372: 2352: 2315: 2280: 2256: 2223: 2172: 2152: 2092: 2057: 2005: 1982: 1944: 1911:is a lambda term, and 1864:operational definition 1837: 1812: 1792: 1772: 1727: 1707: 1687: 1622: 1511: 1487: 1443: 1361: 1308:This method, known as 1299: 1235: 1170: 1115: 1083: 1042: 983: 915: 825:example, the function 802:eeny, meeny, miny, moe 798: 775: 764: 763:{\displaystyle \land } 744: 721: 698:, by first modifying “ 688: 616:logically inconsistent 476: 393: 312: 292: 272: 252: 238:, applying a function 228: 194: 170: 146: 105: 16726:Models of computation 16570:Plural quantification 16464:Inquisitive semantics 16429:Alternative semantics 15852:Kolmogorov complexity 15805:Computably enumerable 15705:Model complete theory 15497:Principia Mathematica 14557:Propositional formula 14386:Banach–Tarski paradox 14097:George Alfred Barnard 14066:Church–Rosser theorem 14061:Frege–Church ontology 13988:Macro Lambda Calculus 13762:10.1145/363744.363749 13616:10.1093/logcom/exi010 13595:Sinot, F.-R. (2005). 13572:10.1007/3540543961_14 13004:"The Lambda Calculus" 12760:Annals of Mathematics 12538:explicit substitution 12428: 12408: 12354: 12328: 12285: 12252: 12202: 12138: 12074: 11930:distributed computing 11662:Bull. Amer. Math. Soc 11500:– An introduction to 11497:To Mock a Mockingbird 11433:Kleene–Rosser paradox 11408:Explicit substitution 11403:programming languages 11231:as first-class values 11213:Typed lambda calculus 11104:evaluation strategies 10926:explicit substitution 10626: 10606: 10444:programming languages 10426: 10405:typed lambda calculus 10399:Typed lambda calculus 10393:Typed lambda calculus 10385:as an alternative to 7452:composed with itself 7414:higher-order function 6020: 5799: 5723: 5694: 5629: 5600: 5535: 5515: 5480: 5442: 5383: 5348: 5302: 5201: 5181: 5128: 5099: 5070: 4966: 4942: 4919: 4770: 4665: 4645: 4625: 4601: 4581: 4561: 4541: 4515: 4427: 4360: 4272: 4248: 4228: 4208: 4188: 4168: 4148: 4122: 4080: 4060: 4040: 4020: 4000: 3952: 3932: 3912: 3892: 3857: 3837: 3817: 3797: 3777: 3749: 3729: 3710: 3681: 3648: 3628: 3608: 3589: 3574:of free variables of 3562: 3542: 3522: 3498:of free variables of 3487: 3467: 3428: 3408: 3388: 3359: 3315: 3246: 3226: 3197: 3168: 3138: 3094: 3062: 3042: 3022: 2972: 2952: 2932: 2912: 2892: 2857: 2819: 2799: 2751: 2731: 2711: 2692: 2640: 2611: 2548: 2503: 2462: 2418: 2373: 2353: 2316: 2281: 2257: 2224: 2173: 2153: 2093: 2058: 2006: 1983: 1945: 1838: 1813: 1793: 1778:// the definition of 1773: 1728: 1708: 1693:// the definition of 1688: 1623: 1512: 1488: 1444: 1362: 1300: 1244:can be reworked into 1236: 1171: 1116: 1084: 1043: 992:(which is read as "a 984: 916: 783: 765: 745: 722: 696:Whitehead and Russell 689: 663: 628:Kleene–Rosser paradox 499:Church–Rosser theorem 477: 394: 313: 293: 273: 253: 229: 195: 171: 147: 106: 16716:Computability theory 16555:Function application 16362:Responsive predicate 16352:Privative adjectives 15800:Church–Turing thesis 15787:Computability theory 14996:continuum hypothesis 14514:Square of opposition 14372:Gödel's completeness 14198:Princeton University 14049:Church–Turing thesis 13905:Georg P. Loczewski, 13784:Scott, Dana (1993). 12417: 12397: 12337: 12302: 12283:{\displaystyle Lx.t} 12265: 12226: 12160: 12127: 11961: 11830:. It does not cover 11820:typed lambda calculi 11352:model of computation 11176:continuous functions 11174:showed that if only 10833:Church–Turing thesis 10827:, respectively and = 10738:model of computation 10615: 10527: 10497:Reduction strategies 10415: 9308:, as it expands to: 9153: where  8640:tests for the value 8545:returns the second. 8204:IFTHENELSE := λ 8093:Logic and predicates 8026:and the other using 7446:, i.e. the function 7159:strongly normalising 6624:reducible expression 6426:. In an expression λ 6096:is a variable, then 5808: 5743: 5703: 5638: 5609: 5544: 5524: 5489: 5451: 5392: 5357: 5353:reduces to the term 5319: 5210: 5190: 5140: 5108: 5079: 4978: 4955: 4931: 4779: 4678: 4654: 4634: 4614: 4590: 4570: 4550: 4524: 4438: 4371: 4280: 4258: 4237: 4217: 4197: 4177: 4157: 4131: 4090: 4069: 4049: 4029: 4009: 3968: 3941: 3921: 3901: 3866: 3846: 3826: 3806: 3786: 3766: 3738: 3718: 3690: 3661: 3637: 3617: 3597: 3578: 3551: 3531: 3502: 3476: 3456: 3417: 3397: 3368: 3339: 3259: 3253:function composition 3235: 3209: 3177: 3151: 3118: 3074: 3051: 3031: 2981: 2961: 2941: 2921: 2901: 2866: 2828: 2808: 2779: 2740: 2720: 2700: 2651: 2620: 2567: 2516: 2471: 2430: 2416:{\displaystyle t(s)} 2398: 2362: 2342: 2290: 2270: 2233: 2182: 2162: 2114: 2100:§ anonymous function 2073: 2028: 1992: 1969: 1919: 1915:is a variable, then 1894:inductive definition 1824: 1802: 1782: 1739: 1717: 1697: 1633: 1528: 1498: 1454: 1374: 1322: 1316:Function application 1251: 1187: 1131: 1099: 1055: 1012: 935: 924:can be rewritten in 832: 818:Computable functions 808:Informal description 754: 731: 702: 669: 526:model of computation 495:repeated application 412: 329: 302: 282: 262: 242: 206: 184: 160: 121: 95: 75:logically consistent 59:model of computation 16640:Cognitive semantics 16605:Strawson entailment 16550:Existential closure 16494:Situation semantics 16397:Temperature paradox 16367:Rising declaratives 16332:Modal subordination 16307:Hurford disjunction 16267:Discourse relations 15954:Mathematical object 15845:P versus NP problem 15810:Computable function 15604:Reverse mathematics 15530:Logical consequence 15407:primitive recursive 15402:elementary function 15175:Free/bound variable 15028:Tarski–Grothendieck 14547:Logical connectives 14477:Logical equivalence 14327:Logical consequence 14132:Stephen Cole Kleene 14087:C. Anthony Anderson 13985:Anton Salikhmetov, 13425:Pierce, Benjamin C. 13271:Sendai, Japan 1997 13159:2008arXiv0804.3434S 12739:Pierce, Benjamin C. 11908:) by Peter Selinger 11604:, vol. 5. Elsevier. 11490:Scott–Curry theorem 11399:Evaluation strategy 11395:for lambda calculus 11387:– Study of certain 10975:Anonymous functions 10726:computable function 10136:can be defined by: 9972:combinator calculus 7651:-th composition of 7635:-th composition of 7623:-th composition of 7464:and is in fact the 7440:-th composition of 6505:, is denoted as FV( 6405:is abbreviated as λ 6086:defined inductively 4120:{\displaystyle y=y} 3998:{\displaystyle x=r} 2977:is the lambda term 2917:; while example 2, 1850:The lambda calculus 1798:has been used with 1713:has been used with 520:Lambda calculus is 227:{\textstyle (M\ N)} 16685:Semantics of logic 16610:Strict conditional 16580:Quantifier raising 16545:Downward entailing 16525:Autonomy of syntax 16454:Generative grammar 16434:Categorial grammar 16372:Scalar implicature 16277:Epistemic modality 16252:De dicto and de re 15752:Transfer principle 15715:Semantics of logic 15700:Categorical theory 15676:Non-standard model 15190:Logical connective 14317:Information theory 14266:Mathematical logic 14162:Hartley Rogers, Jr 14127:John George Kemeny 13940:2021-05-02 at the 13928:2012-10-14 at the 13091:. Lambda-bound.com 12964:Partee, B. B. H.; 12794:Kleene, Stephen C. 12423: 12403: 12349: 12323: 12280: 12247: 12197: 12133: 12069: 11596:2021-05-06 at the 11379:De Bruijn notation 11320:Mathematics portal 11250:Lambda-mu calculus 11079:("delegates") and 10981:Anonymous function 10963:As pointed out by 10881:in the expression 10621: 10601: 10471:mathematical logic 10421: 10275:grab the argument 9648:4 × (3 × (2 × (G ( 9058:F := G G = (λ 8854:be not defined in 8749:programming idioms 8702:can be defined as 7825:since multiplying 7629:composed with the 7180:Encoding datatypes 7163:weakly normalising 7129:local completeness 7068:local reducibility 6857:in the expression 6774:variable shadowing 6654:; the reduct of (λ 6109:is a variable and 6015: 5794: 5718: 5689: 5624: 5595: 5530: 5510: 5475: 5437: 5378: 5343: 5297: 5196: 5176: 5123: 5104:into the identity 5094: 5065: 4961: 4937: 4914: 4765: 4660: 4640: 4620: 4596: 4576: 4556: 4536: 4510: 4422: 4355: 4270:{\displaystyle (t} 4267: 4243: 4223: 4203: 4183: 4163: 4143: 4117: 4075: 4055: 4035: 4015: 3995: 3947: 3927: 3907: 3887: 3852: 3832: 3812: 3792: 3772: 3744: 3724: 3705: 3676: 3643: 3623: 3603: 3584: 3557: 3537: 3517: 3482: 3462: 3423: 3403: 3383: 3354: 3310: 3255:can be defined as 3241: 3221: 3192: 3163: 3133: 3109:first class values 3089: 3057: 3037: 3017: 2967: 2947: 2927: 2907: 2887: 2852: 2814: 2794: 2746: 2726: 2706: 2687: 2635: 2606: 2543: 2498: 2457: 2413: 2368: 2348: 2311: 2276: 2252: 2219: 2168: 2148: 2088: 2053: 2004:{\displaystyle s)} 2001: 1981:{\displaystyle (t} 1978: 1940: 1833: 1808: 1788: 1768: 1723: 1703: 1683: 1618: 1507: 1483: 1439: 1357: 1295: 1231: 1166: 1111: 1079: 1038: 979: 911: 792:, Hilbert had the 760: 740: 717: 684: 501:it will produce a 491:De Bruijn indexing 472: 389: 308: 288: 268: 248: 224: 190: 166: 154:lambda abstraction 142: 101: 41:based on function 35:mathematical logic 16711:1936 in computing 16693: 16692: 16665:Logic translation 16628: 16627: 16620:Universal grinder 16600:Squiggle operator 16560:Meaning postulate 16499:Supervaluationism 16469:Intensional logic 16449:Dynamic semantics 16410: 16409: 16242:Crossover effects 16191:Tense–aspect–mood 16171:Lexical semantics 15990: 15989: 15922:Abstract category 15725:Theories of truth 15535:Rule of inference 15525:Natural deduction 15506: 15505: 15051: 15050: 14756:Cartesian product 14661: 14660: 14567:Many-valued logic 14542:Boolean functions 14425:Russell's paradox 14400:diagonal argument 14297:First-order logic 14232: 14231: 14167:J. Barkley Rosser 13935:Safalra's Website 13889:David C. Keenan, 13873:"Lambda-calculus" 13633:. pp. 1–10. 13484:978-3-540-00326-7 13345:978-3-319-08917-1 13212:978-0-262-20175-9 13036:. (See also this 12702:978-0-521-78098-8 12687:Mitchell, John C. 12672:978-1-4020-5957-5 12662:Computing Meaning 12426:{\displaystyle N} 12406:{\displaystyle M} 12209:from Knowledge's 12059: 12041: 12023: 12014: 11824:pure type systems 11732:978-0-486-28029-5 11682:Kleene, Stephen, 11655:by Alonzo Church" 11640:978-0-691-08394-0 11502:combinatory logic 11275:Combinatory logic 11049:function pointers 10944:Optimal reduction 10819:corresponding to 10697:Optimal reduction 10634:Full β-reductions 10624:{\displaystyle y} 10519:Applicative order 10483:internal language 10383:B, C, K, W system 9657:4 × (3 × (2 × ((λ 8848:is that the name 8673:) (deal_with_nil) 8646:NIL := FALSE 8495:− 1 function for 8294:is equivalent to 7490:laws of exponents 7133:natural deduction 7072:natural deduction 6744:could result in λ 6575:combinatory logic 6037:Formal definition 5533:{\displaystyle s} 5513:{\displaystyle t} 5381:{\displaystyle t} 5199:{\displaystyle z} 4964:{\displaystyle r} 4940:{\displaystyle y} 4663:{\displaystyle r} 4643:{\displaystyle y} 4623:{\displaystyle r} 4599:{\displaystyle y} 4579:{\displaystyle r} 4559:{\displaystyle y} 4246:{\displaystyle y} 4226:{\displaystyle x} 4206:{\displaystyle y} 4186:{\displaystyle x} 4166:{\displaystyle r} 4078:{\displaystyle r} 4058:{\displaystyle x} 4038:{\displaystyle x} 4018:{\displaystyle r} 3950:{\displaystyle t} 3930:{\displaystyle x} 3910:{\displaystyle r} 3890:{\displaystyle t} 3855:{\displaystyle y} 3835:{\displaystyle x} 3815:{\displaystyle r} 3795:{\displaystyle s} 3775:{\displaystyle t} 3747:{\displaystyle y} 3727:{\displaystyle x} 3646:{\displaystyle s} 3626:{\displaystyle t} 3606:{\displaystyle s} 3587:{\displaystyle t} 3560:{\displaystyle x} 3540:{\displaystyle t} 3485:{\displaystyle x} 3465:{\displaystyle x} 3426:{\displaystyle y} 3406:{\displaystyle x} 3333:alpha equivalence 3327:Alpha equivalence 3244:{\displaystyle y} 3204:constant function 3145:identity function 3069:identity function 3060:{\displaystyle x} 3040:{\displaystyle N} 2970:{\displaystyle M} 2950:{\displaystyle N} 2930:{\displaystyle M} 2910:{\displaystyle x} 2817:{\displaystyle B} 2749:{\displaystyle N} 2729:{\displaystyle M} 2709:{\displaystyle x} 2371:{\displaystyle s} 2351:{\displaystyle t} 2279:{\displaystyle f} 2171:{\displaystyle f} 1860:equational theory 1811:{\displaystyle 2} 1791:{\displaystyle y} 1726:{\displaystyle 5} 1706:{\displaystyle x} 714: 681: 438: 318:are lambda terms. 217: 169:{\displaystyle x} 22:(also written as 16738: 16670:Linguistics wars 16595:Semantic parsing 16484:Montague grammar 16419: 16418: 16262:Deontic modality 16116: 16115: 16103:Truth conditions 16038:Compositionality 16031:Central concepts 16017: 16010: 16003: 15994: 15993: 15981: 15980: 15932:History of logic 15927:Category of sets 15820:Decision problem 15599:Ordinal analysis 15540:Sequent calculus 15438:Boolean algebras 15378: 15377: 15352: 15323:logical/constant 15077: 15076: 15063: 14986:Zermelo–Fraenkel 14737:Set operations: 14672: 14671: 14609: 14440: 14439: 14420:Löwenheim–Skolem 14307:Formal semantics 14259: 14252: 14245: 14236: 14235: 14182:Raymond Smullyan 14157:Nicholas Rescher 14152:Michael O. Rabin 14018: 14011: 14004: 13995: 13994: 13975:"Lambda Calculi" 13886: 13845: 13844: 13842: 13840: 13822: 13816: 13814: 13812: 13811: 13799:(1–2): 411–440. 13790: 13781: 13775: 13774: 13764: 13737: 13731: 13730: 13728: 13716: 13707: 13706: 13704: 13680: 13671: 13670: 13642: 13626: 13620: 13619: 13601: 13592: 13586: 13585: 13565: 13545: 13539: 13538: 13536: 13534: 13529: 13511: 13502: 13496: 13495: 13493: 13491: 13464: 13455: 13449: 13448: 13421: 13415: 13412: 13406: 13405: 13403: 13401: 13372: 13363: 13357: 13356: 13354: 13352: 13317: 13308: 13302: 13301: 13299: 13297: 13291: 13282: 13276: 13265: 13256: 13254: 13252: 13245: 13234: 13228: 13222: 13216: 13215: 13198: 13192: 13191: 13168: 13162: 13161: 13152: 13142: 13131: 13122: 13121: 13106: 13100: 13099: 13097: 13096: 13085: 13076: 13070: 13047: 13041: 13026: 13020: 13019: 13017: 13015: 12999: 12993: 12992: 12990: 12988: 12961: 12955: 12954: 12915: 12909: 12908: 12877: 12868: 12867: 12832: 12826: 12825: 12790: 12784: 12783: 12752: 12746: 12745: 12735: 12729: 12728: 12714: 12708: 12706: 12683: 12677: 12676: 12656: 12650: 12649: 12629: 12623: 12622: 12620: 12618: 12603:Coquand, Thierry 12599: 12593: 12592: 12553: 12547: 12535: 12529: 12528: 12527: 12517:Barendregt, Henk 12513: 12479: 12473: 12464: 12458: 12453: 12447: 12439: 12433: 12432: 12430: 12429: 12424: 12412: 12410: 12409: 12404: 12391: 12385: 12378: 12372: 12366: 12360: 12358: 12356: 12355: 12350: 12332: 12330: 12329: 12324: 12298:The lambda term 12296: 12290: 12289: 12287: 12286: 12281: 12256: 12254: 12253: 12248: 12221: 12215: 12206: 12204: 12203: 12198: 12154: 12148: 12142: 12140: 12139: 12134: 12122: 12113: 12110: 12104: 12093: 12080: 12078: 12076: 12075: 12070: 12057: 12039: 12021: 12012: 11955: 11916:by Marius Buliga 11852: 11779: 11736: 11679: 11677: 11659: 11647:Frink Jr., Orrin 11633: 11631: 11630: 11607:Church, Alonzo, 11428:Interaction nets 11322: 11317: 11316: 11101:nondeterministic 11083:, among others. 11065:Wolfram Language 11031: 11027: 11023: 11016: 11013: 11010: 11007: 11004: 11001: 10998: 10995: 10985:For example, in 10922:Director strings 10919: 10898: 10892: 10886: 10880: 10861: 10851: 10814: 10808: 10802: 10792: 10723: 10719: 10688: 10673: 10630: 10628: 10627: 10622: 10610: 10608: 10607: 10602: 10430: 10428: 10427: 10422: 10364: 10335:The combinators 10323: 10317: 10311: 10292: 10286: 10254: 10236: 10222: 10202: 10186: 10169: 10154: 10148: 10131: 10117: 10107: 10094: 10082: 10050: 10044: 10034: 10030: 10026: 10015: 10001: 9995: 9989: 9983: 9976:the next section 9969: 9963: 9957: 9949: 9938: 9912: 9887: 9858: 9827: 9808: 9774: 9749: 9740: 9735: 9730: 9721: 9720:−1)))) (1−1))))) 9696: 9687: 9678: 9653: 9644: 9635: 9610: 9601: 9592: 9567: 9558: 9549: 9524: 9491: 9482: 9463: 9449: 9434: 9396: 9361: 9319: 9307: 9301: 9289: 9245: 9234: 9230: 9226: 9218: 9207: 9183: 9152: 9142: 9131: 9107: 9070: 9049: 9042: 9015: 8981: 8967: 8944: 8925: 8879: 8875: 8867: 8853: 8847: 8833: 8827: 8816: 8802: 8796: 8777: 8738: 8720: 8715:) (SUCC (SECOND 8701: 8689: 8674: 8665:.deal_with_head_ 8648:, the construct 8647: 8643: 8639: 8635: 8628: 8607: 8598: 8589:SECOND := λ 8585: 8572: 8544: 8540: 8536: 8530: 8524: 8516: 8512: 8500: 8494: 8488: 8451: 8409: 8405: 8398: 8388: 8378: 8364: 8339: 8326:ISZERO := λ 8320: 8316: 8312: 8309:, which returns 8308: 8297: 8293: 8290:and we see that 8284: 8263: 8236: 8226: 8200: 8187: 8165: 8138: 8122: 8104: 8100: 8088: 8084: 8074: 8064: 8051: 8021: 8017: 8010: 7982: 7952: 7894: 7890: 7884: 7869: 7848: 7842: 7836: 7830: 7821: 7795: 7762: 7740: 7734: 7728: 7719: 7709: 7702: 7696: 7656: 7650: 7640: 7634: 7628: 7622: 7613: 7580: 7574: 7567: 7555: 7516: 7512: 7504: 7495: 7487: 7481: 7475: 7469: 7463: 7457: 7451: 7445: 7439: 7433: 7427: 7421: 7408: 7384: 7364: 7349: 7326: 7298: 7274: 7255: 7063:× 2) 7 → 7 × 2. 6991:) to result in λ 6977:above for the FV 6861:with expression 6561: 6438:is often called 6282: 6279: 6276: 6272: 6269: 6266: 6263: 6260: 6257: 6253: 6250: 6247: 6244: 6241: 6238: 6234: 6231: 6228: 6224: 6221: 6218: 6215: 6212: 6209: 6205: 6202: 6199: 6195: 6192: 6189: 6185: 6182: 6179: 6171:Backus–Naur form 6148: 6140: 6127: 6115: 6102: 6083: 6024: 6022: 6021: 6016: 5803: 5801: 5800: 5795: 5727: 5725: 5724: 5719: 5698: 5696: 5695: 5690: 5633: 5631: 5630: 5625: 5604: 5602: 5601: 5596: 5539: 5537: 5536: 5531: 5519: 5517: 5516: 5511: 5484: 5482: 5481: 5476: 5446: 5444: 5443: 5438: 5387: 5385: 5384: 5379: 5352: 5350: 5349: 5344: 5306: 5304: 5303: 5298: 5205: 5203: 5202: 5197: 5185: 5183: 5182: 5177: 5132: 5130: 5129: 5124: 5103: 5101: 5100: 5095: 5074: 5072: 5071: 5066: 4970: 4968: 4967: 4962: 4946: 4944: 4943: 4938: 4923: 4921: 4920: 4915: 4774: 4772: 4771: 4766: 4669: 4667: 4666: 4661: 4649: 4647: 4646: 4641: 4629: 4627: 4626: 4621: 4605: 4603: 4602: 4597: 4585: 4583: 4582: 4577: 4565: 4563: 4562: 4557: 4545: 4543: 4542: 4537: 4519: 4517: 4516: 4511: 4431: 4429: 4428: 4423: 4364: 4362: 4361: 4356: 4276: 4274: 4273: 4268: 4252: 4250: 4249: 4244: 4232: 4230: 4229: 4224: 4212: 4210: 4209: 4204: 4192: 4190: 4189: 4184: 4173:substituted for 4172: 4170: 4169: 4164: 4152: 4150: 4149: 4144: 4126: 4124: 4123: 4118: 4084: 4082: 4081: 4076: 4064: 4062: 4061: 4056: 4044: 4042: 4041: 4036: 4025:substituted for 4024: 4022: 4021: 4016: 4004: 4002: 4001: 3996: 3959:capture-avoiding 3956: 3954: 3953: 3948: 3936: 3934: 3933: 3928: 3916: 3914: 3913: 3908: 3896: 3894: 3893: 3888: 3861: 3859: 3858: 3853: 3841: 3839: 3838: 3833: 3821: 3819: 3818: 3813: 3801: 3799: 3798: 3793: 3781: 3779: 3778: 3773: 3753: 3751: 3750: 3745: 3733: 3731: 3730: 3725: 3714: 3712: 3711: 3706: 3685: 3683: 3682: 3677: 3652: 3650: 3649: 3644: 3632: 3630: 3629: 3624: 3612: 3610: 3609: 3604: 3593: 3591: 3590: 3585: 3566: 3564: 3563: 3558: 3546: 3544: 3543: 3538: 3526: 3524: 3523: 3518: 3491: 3489: 3488: 3483: 3471: 3469: 3468: 3463: 3432: 3430: 3429: 3424: 3412: 3410: 3409: 3404: 3392: 3390: 3389: 3384: 3363: 3361: 3360: 3355: 3319: 3317: 3316: 3311: 3250: 3248: 3247: 3242: 3230: 3228: 3227: 3222: 3201: 3199: 3198: 3193: 3172: 3170: 3169: 3164: 3142: 3140: 3139: 3134: 3098: 3096: 3095: 3090: 3066: 3064: 3063: 3058: 3046: 3044: 3043: 3038: 3026: 3024: 3023: 3018: 2976: 2974: 2973: 2968: 2956: 2954: 2953: 2948: 2936: 2934: 2933: 2928: 2916: 2914: 2913: 2908: 2896: 2894: 2893: 2888: 2861: 2859: 2858: 2853: 2823: 2821: 2820: 2815: 2803: 2801: 2800: 2795: 2764: 2755: 2753: 2752: 2747: 2735: 2733: 2732: 2727: 2715: 2713: 2712: 2707: 2696: 2694: 2693: 2688: 2644: 2642: 2641: 2636: 2615: 2613: 2612: 2607: 2556: 2552: 2550: 2549: 2544: 2511: 2507: 2505: 2504: 2499: 2466: 2464: 2463: 2458: 2422: 2420: 2419: 2414: 2393: 2389: 2385: 2381: 2377: 2375: 2374: 2369: 2357: 2355: 2354: 2349: 2331: 2327: 2320: 2318: 2317: 2312: 2285: 2283: 2282: 2277: 2265: 2261: 2259: 2258: 2253: 2245: 2244: 2228: 2226: 2225: 2220: 2209: 2208: 2177: 2175: 2174: 2169: 2157: 2155: 2154: 2149: 2138: 2137: 2109: 2105: 2097: 2095: 2094: 2089: 2062: 2060: 2059: 2054: 2049: 2048: 2010: 2008: 2007: 2002: 1987: 1985: 1984: 1979: 1964: 1960: 1949: 1947: 1946: 1941: 1914: 1910: 1903: 1842: 1840: 1839: 1836:{\textstyle =29} 1834: 1817: 1815: 1814: 1809: 1797: 1795: 1794: 1789: 1777: 1775: 1774: 1769: 1767: 1766: 1754: 1753: 1732: 1730: 1729: 1724: 1712: 1710: 1709: 1704: 1692: 1690: 1689: 1684: 1670: 1669: 1657: 1656: 1627: 1625: 1624: 1619: 1608: 1607: 1592: 1591: 1582: 1581: 1569: 1568: 1544: 1543: 1537: 1536: 1516: 1514: 1513: 1510:{\textstyle =29} 1508: 1492: 1490: 1489: 1484: 1482: 1481: 1469: 1468: 1448: 1446: 1445: 1440: 1420: 1419: 1407: 1406: 1366: 1364: 1363: 1358: 1356: 1304: 1302: 1301: 1296: 1291: 1290: 1278: 1277: 1240: 1238: 1237: 1232: 1230: 1229: 1217: 1216: 1175: 1173: 1172: 1167: 1165: 1120: 1118: 1117: 1112: 1088: 1086: 1085: 1080: 1047: 1045: 1044: 1039: 1037: 1036: 1024: 1023: 1003: 999: 988: 986: 985: 980: 978: 977: 965: 964: 920: 918: 917: 912: 910: 909: 897: 896: 866: 794:epsilon operator 788:Russell had the 769: 767: 766: 761: 749: 747: 746: 741: 726: 724: 723: 718: 716: 715: 707: 693: 691: 690: 685: 683: 682: 674: 643:Richard Montague 584:computer science 536:a variable in a 481: 479: 478: 473: 436: 398: 396: 395: 390: 317: 315: 314: 309: 297: 295: 294: 289: 277: 275: 274: 269: 257: 255: 254: 249: 233: 231: 230: 225: 215: 199: 197: 196: 191: 175: 173: 172: 167: 151: 149: 148: 143: 110: 108: 107: 102: 16746: 16745: 16741: 16740: 16739: 16737: 16736: 16735: 16706:Lambda calculus 16696: 16695: 16694: 16689: 16624: 16513: 16474:Lambda calculus 16406: 16377:Sloppy identity 16337:Opaque contexts 16272:Donkey anaphora 16237:Counterfactuals 16205: 16107: 16026: 16021: 15991: 15986: 15975: 15968: 15913:Category theory 15903:Algebraic logic 15886: 15857:Lambda calculus 15795:Church encoding 15781: 15757:Truth predicate 15613: 15579:Complete theory 15502: 15371: 15367: 15363: 15358: 15350: 15070: and  15066: 15061: 15047: 15023:New Foundations 14991:axiom of choice 14974: 14936:Gödel numbering 14876: and  14868: 14772: 14657: 14607: 14588: 14537:Boolean algebra 14523: 14487:Equiconsistency 14452:Classical logic 14429: 14410:Halting problem 14398: and  14374: and  14362: and  14361: 14356:Theorems ( 14351: 14268: 14263: 14233: 14228: 14207: 14186: 14137:Simon B. Kochen 14070: 14054:Church encoding 14039:Lambda calculus 14027: 14022: 13959:Lambda Animator 13942:Wayback Machine 13930:Wayback Machine 13923:Lambda Calculus 13871: 13863:Helmut Brandl, 13858:Lambda Calculus 13856:Graham Hutton, 13853: 13848: 13838: 13836: 13824: 13823: 13819: 13809: 13807: 13788: 13782: 13778: 13738: 13734: 13717: 13710: 13681: 13674: 13659: 13627: 13623: 13599: 13593: 13589: 13582: 13563:10.1.1.139.6913 13546: 13542: 13532: 13530: 13509: 13503: 13499: 13489: 13487: 13485: 13462: 13456: 13452: 13445: 13422: 13418: 13413: 13409: 13399: 13397: 13370: 13364: 13360: 13350: 13348: 13346: 13315: 13309: 13305: 13295: 13293: 13289: 13285:Ker, Andrew D. 13283: 13279: 13266: 13259: 13250: 13243: 13235: 13231: 13223: 13219: 13213: 13199: 13195: 13169: 13165: 13140: 13132: 13125: 13108: 13107: 13103: 13094: 13092: 13087: 13086: 13079: 13067: 13048: 13044: 13027: 13023: 13013: 13011: 13000: 12996: 12986: 12984: 12982: 12962: 12958: 12935:10.2307/2266170 12916: 12912: 12897:10.2307/2371045 12878: 12871: 12856:10.2307/2268117 12833: 12829: 12814:10.2307/1968646 12791: 12787: 12772:10.2307/1968337 12753: 12749: 12736: 12732: 12715: 12711: 12703: 12684: 12680: 12673: 12657: 12653: 12646: 12630: 12626: 12616: 12614: 12600: 12596: 12573:10.2307/2268280 12557:Turing, Alan M. 12554: 12550: 12536: 12532: 12525: 12514: 12505: 12488: 12483: 12482: 12476:§ call-by-value 12471: 12465: 12461: 12451: 12441: 12440: 12436: 12418: 12415: 12414: 12398: 12395: 12394: 12392: 12388: 12379: 12375: 12367: 12363: 12338: 12335: 12334: 12303: 12300: 12299: 12297: 12293: 12266: 12263: 12262: 12227: 12224: 12223: 12222: 12218: 12161: 12158: 12157: 12155: 12151: 12143:is pronounced " 12128: 12125: 12124: 12123: 12116: 12111: 12107: 12094: 12083: 11962: 11959: 11958: 11956: 11952: 11947: 11926:graph reduction 11896:) by Raúl Rojas 11884:) by Dana Scott 11872:) by Achim Jung 11850: 11784:Hankin, Chris, 11733: 11657: 11628: 11626: 11598:Wayback Machine 11571:pp1091–1132 of 11527: 11525:Further reading 11522: 11484:virtual machine 11451:Krivine machine 11373:De Bruijn index 11343:category theory 11331:– Treatment of 11318: 11311: 11308: 11254:classical logic 11202: 11124: 11116:process calculi 11089: 11029: 11025: 11021: 11018: 11017: 11014: 11011: 11008: 11005: 11002: 10999: 10996: 10993: 10983: 10977: 10961: 10915: 10894: 10888: 10882: 10876: 10868: 10857: 10847: 10844:Gödel numbering 10830: 10817:Church numerals 10810: 10804: 10798: 10796: 10788: 10784:if and only if 10742:Turing complete 10721: 10717: 10714: 10675: 10656: 10649:substituted in. 10616: 10613: 10612: 10528: 10525: 10524: 10505: 10499: 10416: 10413: 10412: 10401: 10395: 10360: 10343:are similar to 10319: 10315: 10305: 10290: 10280: 10250: 10232: 10218: 10198: 10187:is not free in 10182: 10165: 10150: 10144: 10127: 10113: 10103: 10088: 10078: 10063: 10057: 10046: 10040: 10032: 10028: 10017: 10007: 9997: 9991: 9985: 9979: 9965: 9959: 9953: 9941: 9915: 9890: 9861: 9830: 9811: 9777: 9762: 9756: 9745: 9738: 9733: 9724: 9699: 9690: 9681: 9677:−1)))) (2−1)))) 9656: 9647: 9638: 9613: 9604: 9595: 9570: 9561: 9552: 9527: 9494: 9485: 9476: 9454: 9437: 9399: 9364: 9322: 9312: 9303: 9294: 9250: 9243: 9232: 9228: 9224: 9216: 9189: 9188:so that  9154: 9151:F := FIX G 9150: 9133: 9113: 9081: 9057: 9044: 9021: 8986: 8977: 8949: 8938: 8909: 8898: 8892: 8886: 8877: 8873: 8863: 8849: 8845: 8831: 8821: 8814: 8811:syntactic sugar 8800: 8790: 8773: 8765: 8763:Named constants 8745: 8728: 8706: 8691: 8679: 8649: 8645: 8641: 8637: 8633: 8610: 8601: 8588: 8576:FIRST := λ 8575: 8549: 8542: 8538: 8532: 8526: 8522: 8521:. For example, 8517:, by using the 8514: 8510: 8507: 8496: 8490: 8456: 8414: 8407: 8403: 8390: 8380: 8370: 8347: 8325: 8318: 8314: 8310: 8306: 8295: 8291: 8282: 8266: 8262:TRUE FALSE TRUE 8261: 8239: 8234: 8203: 8190: 8168: 8146: 8126:FALSE := λ 8125: 8109: 8102: 8098: 8095: 8086: 8076: 8066: 8056: 8034: 8019: 8012: 7984: 7961: 7899: 7892: 7886: 7874: 7853: 7844: 7838: 7832: 7826: 7803: 7770: 7745: 7736: 7730: 7724: 7717: 7707: 7700: 7661: 7652: 7642: 7636: 7630: 7624: 7618: 7585: 7576: 7569: 7563: 7537: 7514: 7510: 7500: 7493: 7483: 7477: 7471: 7465: 7459: 7453: 7447: 7441: 7435: 7429: 7423: 7417: 7387: 7367: 7352: 7340: 7301: 7277: 7258: 7242: 7236:Church numerals 7232:natural numbers 7228: 7192: 7186:Church encoding 7184:Main articles: 7182: 7151: 7145: 7084: 7027: 6920: 6914: 6907: 6901: 6843: 6835:De Bruijn index 6816:name resolution 6756:, but it could 6699: 6677:is not free in 6583: 6547: 6420: 6290: 6285: 6284: 6280: 6277: 6274: 6270: 6267: 6264: 6261: 6258: 6255: 6251: 6248: 6245: 6242: 6239: 6236: 6232: 6229: 6226: 6222: 6219: 6216: 6213: 6210: 6207: 6203: 6200: 6197: 6193: 6190: 6187: 6183: 6180: 6177: 6142: 6131: 6117: 6110: 6097: 6081: 6076:parentheses (). 6069: 6062: 6050: 6045: 6039: 5809: 5806: 5805: 5744: 5741: 5740: 5704: 5701: 5700: 5639: 5636: 5635: 5610: 5607: 5606: 5545: 5542: 5541: 5525: 5522: 5521: 5490: 5487: 5486: 5452: 5449: 5448: 5393: 5390: 5389: 5388:. The notation 5358: 5355: 5354: 5320: 5317: 5316: 5313: 5211: 5208: 5207: 5191: 5188: 5187: 5141: 5138: 5137: 5109: 5106: 5105: 5080: 5077: 5076: 4979: 4976: 4975: 4956: 4953: 4952: 4932: 4929: 4928: 4780: 4777: 4776: 4679: 4676: 4675: 4655: 4652: 4651: 4635: 4632: 4631: 4615: 4612: 4611: 4606:is said to be " 4591: 4588: 4587: 4571: 4568: 4567: 4551: 4548: 4547: 4525: 4522: 4521: 4439: 4436: 4435: 4372: 4369: 4368: 4281: 4278: 4277: 4259: 4256: 4255: 4238: 4235: 4234: 4218: 4215: 4214: 4198: 4195: 4194: 4178: 4175: 4174: 4158: 4155: 4154: 4132: 4129: 4128: 4091: 4088: 4087: 4070: 4067: 4066: 4050: 4047: 4046: 4030: 4027: 4026: 4010: 4007: 4006: 3969: 3966: 3965: 3942: 3939: 3938: 3922: 3919: 3918: 3902: 3899: 3898: 3867: 3864: 3863: 3847: 3844: 3843: 3827: 3824: 3823: 3807: 3804: 3803: 3787: 3784: 3783: 3767: 3764: 3763: 3760: 3739: 3736: 3735: 3719: 3716: 3715: 3691: 3688: 3687: 3662: 3659: 3658: 3638: 3635: 3634: 3618: 3615: 3614: 3598: 3595: 3594: 3579: 3576: 3575: 3552: 3549: 3548: 3532: 3529: 3528: 3503: 3500: 3499: 3477: 3474: 3473: 3457: 3454: 3453: 3442: 3418: 3415: 3414: 3398: 3395: 3394: 3369: 3366: 3365: 3340: 3337: 3336: 3329: 3260: 3257: 3256: 3236: 3233: 3232: 3210: 3207: 3206: 3202:represents the 3178: 3175: 3174: 3152: 3149: 3148: 3143:represents the 3119: 3116: 3115: 3105: 3075: 3072: 3071: 3052: 3049: 3048: 3032: 3029: 3028: 2982: 2979: 2978: 2962: 2959: 2958: 2942: 2939: 2938: 2922: 2919: 2918: 2902: 2899: 2898: 2867: 2864: 2863: 2829: 2826: 2825: 2809: 2806: 2805: 2780: 2777: 2776: 2762: 2741: 2738: 2737: 2721: 2718: 2717: 2701: 2698: 2697: 2652: 2649: 2648: 2621: 2618: 2617: 2568: 2565: 2564: 2554: 2517: 2514: 2513: 2509: 2472: 2469: 2468: 2431: 2428: 2427: 2399: 2396: 2395: 2391: 2387: 2383: 2379: 2363: 2360: 2359: 2343: 2340: 2339: 2329: 2325: 2291: 2288: 2287: 2271: 2268: 2267: 2263: 2240: 2236: 2234: 2231: 2230: 2229:using the term 2204: 2200: 2183: 2180: 2179: 2163: 2160: 2159: 2133: 2129: 2115: 2112: 2111: 2110:. For example, 2107: 2103: 2074: 2071: 2070: 2044: 2040: 2029: 2026: 2025: 1993: 1990: 1989: 1970: 1967: 1966: 1962: 1958: 1920: 1917: 1916: 1912: 1908: 1901: 1879: 1852: 1825: 1822: 1821: 1803: 1800: 1799: 1783: 1780: 1779: 1762: 1758: 1749: 1745: 1740: 1737: 1736: 1718: 1715: 1714: 1698: 1695: 1694: 1665: 1661: 1652: 1648: 1634: 1631: 1630: 1603: 1602: 1587: 1586: 1577: 1573: 1564: 1560: 1539: 1538: 1532: 1531: 1529: 1526: 1525: 1499: 1496: 1495: 1477: 1473: 1464: 1460: 1455: 1452: 1451: 1415: 1411: 1402: 1398: 1375: 1372: 1371: 1325: 1323: 1320: 1319: 1286: 1282: 1273: 1269: 1252: 1249: 1248: 1225: 1221: 1212: 1208: 1188: 1185: 1184: 1134: 1132: 1129: 1128: 1100: 1097: 1096: 1056: 1053: 1052: 1032: 1028: 1019: 1015: 1013: 1010: 1009: 1001: 997: 973: 969: 960: 956: 936: 933: 932: 905: 901: 892: 888: 835: 833: 830: 829: 815: 810: 755: 752: 751: 732: 729: 728: 706: 705: 703: 700: 699: 673: 672: 670: 667: 666: 655: 604: 596:category theory 522:Turing complete 518: 413: 410: 409: 404:name collisions 330: 327: 326: 303: 300: 299: 283: 280: 279: 263: 260: 259: 258:to an argument 243: 240: 239: 207: 204: 203: 185: 182: 181: 161: 158: 157: 122: 119: 118: 96: 93: 92: 84:and performing 49:using variable 37:for expressing 20:Lambda calculus 17: 12: 11: 5: 16744: 16734: 16733: 16728: 16723: 16721:Formal methods 16718: 16713: 16708: 16691: 16690: 16688: 16687: 16682: 16677: 16672: 16667: 16662: 16660:Inferentialism 16657: 16655:Formal grammar 16652: 16647: 16642: 16636: 16634: 16630: 16629: 16626: 16625: 16623: 16622: 16617: 16612: 16607: 16602: 16597: 16592: 16587: 16582: 16577: 16575:Possible world 16572: 16567: 16562: 16557: 16552: 16547: 16542: 16537: 16532: 16527: 16521: 16519: 16515: 16514: 16512: 16511: 16506: 16501: 16496: 16491: 16486: 16481: 16476: 16471: 16466: 16461: 16459:Glue semantics 16456: 16451: 16446: 16441: 16436: 16431: 16425: 16423: 16422:Formal systems 16416: 16412: 16411: 16408: 16407: 16405: 16404: 16399: 16394: 16389: 16384: 16379: 16374: 16369: 16364: 16359: 16354: 16349: 16347:Polarity items 16344: 16339: 16334: 16329: 16324: 16319: 16314: 16309: 16304: 16299: 16294: 16289: 16284: 16279: 16274: 16269: 16264: 16259: 16254: 16249: 16244: 16239: 16234: 16232:Conservativity 16229: 16224: 16219: 16213: 16211: 16207: 16206: 16204: 16203: 16198: 16196:Quantification 16193: 16188: 16183: 16178: 16173: 16168: 16163: 16158: 16153: 16148: 16143: 16138: 16133: 16128: 16122: 16120: 16113: 16109: 16108: 16106: 16105: 16100: 16095: 16090: 16085: 16080: 16075: 16073:Presupposition 16070: 16065: 16060: 16055: 16050: 16045: 16040: 16034: 16032: 16028: 16027: 16020: 16019: 16012: 16005: 15997: 15988: 15987: 15973: 15970: 15969: 15967: 15966: 15961: 15956: 15951: 15946: 15945: 15944: 15934: 15929: 15924: 15915: 15910: 15905: 15900: 15898:Abstract logic 15894: 15892: 15888: 15887: 15885: 15884: 15879: 15877:Turing machine 15874: 15869: 15864: 15859: 15854: 15849: 15848: 15847: 15842: 15837: 15832: 15827: 15817: 15815:Computable set 15812: 15807: 15802: 15797: 15791: 15789: 15783: 15782: 15780: 15779: 15774: 15769: 15764: 15759: 15754: 15749: 15744: 15743: 15742: 15737: 15732: 15722: 15717: 15712: 15710:Satisfiability 15707: 15702: 15697: 15696: 15695: 15685: 15684: 15683: 15673: 15672: 15671: 15666: 15661: 15656: 15651: 15641: 15640: 15639: 15634: 15627:Interpretation 15623: 15621: 15615: 15614: 15612: 15611: 15606: 15601: 15596: 15591: 15581: 15576: 15575: 15574: 15573: 15572: 15562: 15557: 15547: 15542: 15537: 15532: 15527: 15522: 15516: 15514: 15508: 15507: 15504: 15503: 15501: 15500: 15492: 15491: 15490: 15489: 15484: 15483: 15482: 15477: 15472: 15452: 15451: 15450: 15448:minimal axioms 15445: 15434: 15433: 15432: 15421: 15420: 15419: 15414: 15409: 15404: 15399: 15394: 15381: 15379: 15360: 15359: 15357: 15356: 15355: 15354: 15342: 15337: 15336: 15335: 15330: 15325: 15320: 15310: 15305: 15300: 15295: 15294: 15293: 15288: 15278: 15277: 15276: 15271: 15266: 15261: 15251: 15246: 15245: 15244: 15239: 15234: 15224: 15223: 15222: 15217: 15212: 15207: 15202: 15197: 15187: 15182: 15177: 15172: 15171: 15170: 15165: 15160: 15155: 15145: 15140: 15138:Formation rule 15135: 15130: 15129: 15128: 15123: 15113: 15112: 15111: 15101: 15096: 15091: 15086: 15080: 15074: 15057:Formal systems 15053: 15052: 15049: 15048: 15046: 15045: 15040: 15035: 15030: 15025: 15020: 15015: 15010: 15005: 15000: 14999: 14998: 14993: 14982: 14980: 14976: 14975: 14973: 14972: 14971: 14970: 14960: 14955: 14954: 14953: 14946:Large cardinal 14943: 14938: 14933: 14928: 14923: 14909: 14908: 14907: 14902: 14897: 14882: 14880: 14870: 14869: 14867: 14866: 14865: 14864: 14859: 14854: 14844: 14839: 14834: 14829: 14824: 14819: 14814: 14809: 14804: 14799: 14794: 14789: 14783: 14781: 14774: 14773: 14771: 14770: 14769: 14768: 14763: 14758: 14753: 14748: 14743: 14735: 14734: 14733: 14728: 14718: 14713: 14711:Extensionality 14708: 14706:Ordinal number 14703: 14693: 14688: 14687: 14686: 14675: 14669: 14663: 14662: 14659: 14658: 14656: 14655: 14650: 14645: 14640: 14635: 14630: 14625: 14624: 14623: 14613: 14612: 14611: 14598: 14596: 14590: 14589: 14587: 14586: 14585: 14584: 14579: 14574: 14564: 14559: 14554: 14549: 14544: 14539: 14533: 14531: 14525: 14524: 14522: 14521: 14516: 14511: 14506: 14501: 14496: 14491: 14490: 14489: 14479: 14474: 14469: 14464: 14459: 14454: 14448: 14446: 14437: 14431: 14430: 14428: 14427: 14422: 14417: 14412: 14407: 14402: 14390:Cantor's  14388: 14383: 14378: 14368: 14366: 14353: 14352: 14350: 14349: 14344: 14339: 14334: 14329: 14324: 14319: 14314: 14309: 14304: 14299: 14294: 14289: 14288: 14287: 14276: 14274: 14270: 14269: 14262: 14261: 14254: 14247: 14239: 14230: 14229: 14227: 14226: 14221: 14215: 14213: 14209: 14208: 14206: 14205: 14200: 14194: 14192: 14188: 14187: 14185: 14184: 14179: 14177:Norman Shapiro 14174: 14169: 14164: 14159: 14154: 14149: 14144: 14142:Maurice L'Abbé 14139: 14134: 14129: 14124: 14119: 14114: 14112:William Easton 14109: 14104: 14099: 14094: 14089: 14084: 14078: 14076: 14072: 14071: 14069: 14068: 14063: 14058: 14057: 14056: 14051: 14046: 14035: 14033: 14029: 14028: 14021: 14020: 14013: 14006: 13998: 13992: 13991: 13983: 13971: 13962: 13955: 13950: 13944: 13919: 13911: 13903: 13895: 13887: 13869: 13861: 13852: 13851:External links 13849: 13847: 13846: 13817: 13776: 13732: 13708: 13672: 13657: 13621: 13610:(2): 201–218. 13587: 13580: 13540: 13497: 13483: 13450: 13443: 13437:. p. 56. 13416: 13407: 13381:(2): 393–413. 13358: 13344: 13303: 13277: 13269:Proc. TACS '94 13257: 13229: 13217: 13211: 13193: 13182:(4): 265–282. 13163: 13123: 13101: 13077: 13065: 13042: 13021: 12994: 12980: 12966:ter Meulen, A. 12956: 12919:Church, Alonzo 12910: 12891:(2): 345–363. 12881:Church, Alonzo 12869: 12850:(4): 170–171. 12836:Church, Alonzo 12827: 12785: 12766:(2): 346–366. 12756:Church, Alonzo 12747: 12730: 12727:on 2023-12-07. 12709: 12701: 12678: 12671: 12651: 12644: 12624: 12594: 12567:(4): 153–163. 12548: 12530: 12502: 12487: 12484: 12481: 12480: 12470:extended with 12459: 12434: 12422: 12402: 12386: 12373: 12361: 12348: 12345: 12342: 12322: 12319: 12316: 12313: 12310: 12307: 12291: 12279: 12276: 12273: 12270: 12246: 12243: 12240: 12237: 12234: 12231: 12216: 12196: 12192: 12189: 12186: 12183: 12180: 12177: 12174: 12171: 12168: 12165: 12149: 12132: 12114: 12105: 12103: 12102: 12081: 12068: 12065: 12062: 12056: 12053: 12050: 12047: 12044: 12038: 12035: 12032: 12029: 12026: 12020: 12017: 12011: 12008: 12005: 12002: 11999: 11996: 11993: 11990: 11987: 11984: 11981: 11978: 11975: 11972: 11969: 11966: 11949: 11948: 11946: 11943: 11942: 11941: 11917: 11909: 11897: 11885: 11873: 11860: 11859: 11855: 11854: 11848: 11835: 11803: 11802: 11800: 11796: 11795: 11782: 11762:(2): 211–247. 11746: 11737: 11731: 11718: 11709: 11691: 11680: 11668:(3): 169–172. 11643: 11616: 11605: 11587: 11565: 11558: 11547: 11526: 11523: 11521: 11520: 11510: 11504: 11493: 11487: 11477: 11471: 11466: 11463:Let expression 11460: 11454: 11448: 11436: 11430: 11425: 11422:Harrop formula 11419: 11414: 11405: 11396: 11382: 11376: 11370: 11361: 11355: 11345: 11336: 11325: 11324: 11323: 11307: 11304: 11303: 11302: 11278: 11268: 11267: 11264:Kappa calculus 11257: 11256: 11247: 11237:formal systems 11233: 11232: 11222: 11216: 11201: 11198: 11170:In the 1970s, 11143:can exist, by 11123: 11120: 11088: 11085: 10992: 10979:Main article: 10976: 10973: 10960: 10957: 10937:size explosion 10910:in the length 10870:The notion of 10867: 10864: 10828: 10803:,  where 10794: 10713: 10710: 10709: 10708: 10704: 10701: 10698: 10691: 10690: 10653: 10650: 10646: 10639: 10638: 10635: 10632: 10620: 10600: 10596: 10593: 10590: 10587: 10584: 10581: 10578: 10575: 10571: 10568: 10565: 10562: 10559: 10556: 10553: 10550: 10545: 10542: 10539: 10536: 10532: 10520: 10517: 10513: 10501:Main article: 10498: 10495: 10485:of classes of 10420: 10397:Main article: 10394: 10391: 10243: 10242: 10192: 10159: 10059:Main article: 10056: 10053: 9970:form complete 9951: 9950: 9939: 9913: 9888: 9859: 9828: 9809: 9775: 9755: 9754:Standard terms 9752: 9742: 9741: 9736: 9731: 9722: 9697: 9688: 9679: 9654: 9645: 9636: 9634:−1)))) (3−1))) 9611: 9602: 9593: 9568: 9559: 9550: 9525: 9492: 9483: 9464:,  where 9451: 9450: 9435: 9397: 9362: 9320: 9291: 9290: 9237:self-reference 9213: 9212: 9211: 9210: 9209: 9208: 9148: 9147: 9146: 9145: 9144: 9072: 9071: 9055: 9054: 9053: 9052: 9051: 8970: 8969: 8888:Main article: 8885: 8882: 8838: 8837: 8807: 8806: 8764: 8761: 8744: 8741: 8740: 8739: 8737:Φ (PAIR 0 0)). 8729:PRED := λ 8722: 8721: 8711:.PAIR (SECOND 8630: 8629: 8611:NULL := λ 8608: 8599: 8586: 8573: 8550:PAIR := λ 8506: 8503: 8453: 8452: 8415:PRED := λ 8367: 8366: 8341: 8340: 8292:AND TRUE FALSE 8288: 8287: 8286: 8285: 8280: 8279:) FALSE TRUE → 8264: 8259: 8258:) TRUE FALSE → 8235:AND TRUE FALSE 8228: 8227: 8201: 8188: 8166: 8140: 8139: 8123: 8110:TRUE := λ 8094: 8091: 8054: 8053: 7954: 7953: 7900:PRED := λ 7871: 7870: 7823: 7822: 7804:MULT := λ 7799:Alternatively 7797: 7796: 7771:MULT := λ 7764: 7763: 7746:PLUS := λ 7721: 7720: 7711: 7710: 7698: 7697: 7662:PLUS := λ 7615: 7614: 7586:SUCC := λ 7557: 7556: 7410: 7409: 7385: 7365: 7350: 7328: 7327: 7299: 7275: 7256: 7227: 7224: 7181: 7178: 7155:rewriting rule 7147:Main article: 7144: 7141: 7099:if and only if 7095:extensionality 7083: 7080: 7026: 7023: 6981: 6980: 6939: 6921: 6918: 6912: 6905: 6899: 6893: 6876: 6842: 6839: 6698: 6695: 6609: 6608: 6602: 6596: 6582: 6579: 6563: 6562: 6545: 6526: 6525:is a variable. 6499:free variables 6419: 6416: 6415: 6414: 6387: 6352: 6335: 6311: 6289: 6286: 6176: 6150: 6149: 6128: 6103: 6078: 6077: 6074: 6071: 6067: 6060: 6049: 6046: 6041:Main article: 6038: 6035: 6014: 6011: 6008: 6005: 6002: 5999: 5996: 5993: 5990: 5987: 5984: 5981: 5978: 5975: 5972: 5969: 5966: 5963: 5960: 5957: 5954: 5951: 5948: 5945: 5942: 5939: 5936: 5933: 5930: 5927: 5924: 5921: 5918: 5915: 5912: 5909: 5906: 5903: 5900: 5897: 5894: 5891: 5888: 5885: 5882: 5879: 5876: 5873: 5870: 5867: 5864: 5861: 5858: 5855: 5852: 5849: 5846: 5843: 5840: 5837: 5834: 5831: 5828: 5825: 5822: 5819: 5816: 5813: 5793: 5790: 5787: 5784: 5781: 5778: 5775: 5772: 5769: 5766: 5763: 5760: 5757: 5754: 5751: 5748: 5717: 5714: 5711: 5708: 5688: 5685: 5682: 5679: 5676: 5673: 5670: 5667: 5664: 5661: 5658: 5655: 5652: 5649: 5646: 5643: 5623: 5620: 5617: 5614: 5594: 5591: 5588: 5585: 5582: 5579: 5576: 5573: 5570: 5567: 5564: 5561: 5558: 5555: 5552: 5549: 5529: 5509: 5506: 5503: 5500: 5497: 5494: 5474: 5471: 5468: 5465: 5462: 5459: 5456: 5436: 5433: 5430: 5427: 5424: 5421: 5418: 5415: 5412: 5409: 5406: 5403: 5400: 5397: 5377: 5374: 5371: 5368: 5365: 5362: 5342: 5339: 5336: 5333: 5330: 5327: 5324: 5312: 5309: 5296: 5293: 5290: 5287: 5284: 5281: 5278: 5275: 5272: 5269: 5266: 5263: 5260: 5257: 5254: 5251: 5248: 5245: 5242: 5239: 5236: 5233: 5230: 5227: 5224: 5221: 5218: 5215: 5195: 5175: 5172: 5169: 5166: 5163: 5160: 5157: 5154: 5151: 5148: 5145: 5122: 5119: 5116: 5113: 5093: 5090: 5087: 5084: 5064: 5061: 5058: 5055: 5052: 5049: 5046: 5043: 5040: 5037: 5034: 5031: 5028: 5025: 5022: 5019: 5016: 5013: 5010: 5007: 5004: 5001: 4998: 4995: 4992: 4989: 4986: 4983: 4960: 4949:free variables 4947:is not in the 4936: 4913: 4910: 4907: 4904: 4901: 4898: 4895: 4892: 4889: 4886: 4883: 4880: 4877: 4874: 4871: 4868: 4865: 4862: 4859: 4856: 4853: 4850: 4847: 4844: 4841: 4838: 4835: 4832: 4829: 4826: 4823: 4820: 4817: 4814: 4811: 4808: 4805: 4802: 4799: 4796: 4793: 4790: 4787: 4784: 4764: 4761: 4758: 4755: 4752: 4749: 4746: 4743: 4740: 4737: 4734: 4731: 4728: 4725: 4722: 4719: 4716: 4713: 4710: 4707: 4704: 4701: 4698: 4695: 4692: 4689: 4686: 4683: 4672: 4671: 4659: 4639: 4619: 4595: 4575: 4555: 4535: 4532: 4529: 4509: 4506: 4503: 4500: 4497: 4494: 4491: 4488: 4485: 4482: 4479: 4476: 4473: 4470: 4467: 4464: 4461: 4458: 4455: 4452: 4449: 4446: 4443: 4433: 4421: 4418: 4415: 4412: 4409: 4406: 4403: 4400: 4397: 4394: 4391: 4388: 4385: 4382: 4379: 4376: 4366: 4354: 4351: 4348: 4345: 4342: 4339: 4336: 4333: 4330: 4327: 4324: 4321: 4318: 4315: 4312: 4309: 4306: 4303: 4300: 4297: 4294: 4291: 4288: 4285: 4266: 4263: 4253: 4242: 4222: 4213:(which is not 4202: 4182: 4162: 4142: 4139: 4136: 4116: 4113: 4110: 4107: 4104: 4101: 4098: 4095: 4085: 4074: 4054: 4034: 4014: 3994: 3991: 3988: 3985: 3982: 3979: 3976: 3973: 3946: 3926: 3906: 3886: 3883: 3880: 3877: 3874: 3871: 3851: 3831: 3811: 3791: 3771: 3759: 3756: 3743: 3723: 3704: 3701: 3698: 3695: 3675: 3672: 3669: 3666: 3655: 3654: 3642: 3622: 3602: 3583: 3568: 3556: 3536: 3516: 3513: 3510: 3507: 3492: 3481: 3461: 3446:free variables 3441: 3440:Free variables 3438: 3422: 3402: 3382: 3379: 3376: 3373: 3353: 3350: 3347: 3344: 3328: 3325: 3309: 3306: 3303: 3300: 3297: 3294: 3291: 3288: 3285: 3282: 3279: 3276: 3273: 3270: 3267: 3264: 3240: 3220: 3217: 3214: 3191: 3188: 3185: 3182: 3162: 3159: 3156: 3132: 3129: 3126: 3123: 3104: 3101: 3088: 3085: 3082: 3079: 3056: 3036: 3016: 3013: 3010: 3007: 3004: 3001: 2998: 2995: 2992: 2989: 2986: 2966: 2946: 2926: 2906: 2886: 2883: 2880: 2877: 2874: 2871: 2851: 2848: 2845: 2842: 2839: 2836: 2833: 2813: 2793: 2790: 2787: 2784: 2758: 2757: 2745: 2725: 2705: 2686: 2683: 2680: 2677: 2674: 2671: 2668: 2665: 2662: 2659: 2656: 2646: 2634: 2631: 2628: 2625: 2605: 2602: 2599: 2596: 2593: 2590: 2587: 2584: 2581: 2578: 2575: 2572: 2542: 2539: 2536: 2533: 2530: 2527: 2524: 2521: 2497: 2494: 2491: 2488: 2485: 2482: 2479: 2476: 2456: 2453: 2450: 2447: 2444: 2441: 2438: 2435: 2412: 2409: 2406: 2403: 2367: 2347: 2310: 2307: 2304: 2301: 2298: 2295: 2275: 2251: 2248: 2243: 2239: 2218: 2215: 2212: 2207: 2203: 2199: 2196: 2193: 2190: 2187: 2167: 2147: 2144: 2141: 2136: 2132: 2128: 2125: 2122: 2119: 2087: 2084: 2081: 2078: 2052: 2047: 2043: 2039: 2036: 2033: 2017: 2016: 2000: 1997: 1977: 1974: 1955: 1939: 1936: 1933: 1930: 1927: 1924: 1905: 1878: 1875: 1851: 1848: 1844: 1843: 1832: 1829: 1819: 1807: 1787: 1765: 1761: 1757: 1752: 1748: 1744: 1734: 1722: 1702: 1682: 1679: 1676: 1673: 1668: 1664: 1660: 1655: 1651: 1647: 1644: 1641: 1638: 1628: 1617: 1614: 1611: 1606: 1601: 1598: 1595: 1590: 1585: 1580: 1576: 1572: 1567: 1563: 1559: 1556: 1553: 1550: 1547: 1542: 1535: 1519: 1518: 1506: 1503: 1493: 1480: 1476: 1472: 1467: 1463: 1459: 1449: 1438: 1435: 1432: 1429: 1426: 1423: 1418: 1414: 1410: 1405: 1401: 1397: 1394: 1391: 1388: 1385: 1382: 1379: 1355: 1352: 1349: 1346: 1343: 1340: 1337: 1334: 1331: 1328: 1306: 1305: 1294: 1289: 1285: 1281: 1276: 1272: 1268: 1265: 1262: 1259: 1256: 1242: 1241: 1228: 1224: 1220: 1215: 1211: 1207: 1204: 1201: 1198: 1195: 1192: 1164: 1161: 1158: 1155: 1152: 1149: 1146: 1143: 1140: 1137: 1122: 1121: 1110: 1107: 1104: 1090: 1089: 1078: 1075: 1072: 1069: 1066: 1063: 1060: 1035: 1031: 1027: 1022: 1018: 990: 989: 976: 972: 968: 963: 959: 955: 952: 949: 946: 943: 940: 926:anonymous form 922: 921: 908: 904: 900: 895: 891: 887: 884: 881: 878: 875: 872: 869: 865: 862: 859: 856: 853: 850: 847: 844: 841: 838: 814: 811: 809: 806: 759: 739: 736: 713: 710: 680: 677: 654: 649:Origin of the 647: 626:developed the 620:Stephen Kleene 603: 600: 530:Turing machine 517: 514: 487: 486: 471: 468: 465: 462: 459: 456: 453: 450: 447: 444: 441: 435: 432: 429: 426: 423: 420: 417: 407: 400:: α-conversion 388: 385: 382: 379: 376: 373: 370: 367: 364: 361: 358: 355: 352: 349: 346: 343: 340: 337: 334: 320: 319: 311:{\textstyle N} 307: 291:{\textstyle M} 287: 271:{\textstyle N} 267: 251:{\textstyle M} 247: 223: 220: 214: 211: 201: 193:{\textstyle M} 189: 165: 141: 138: 135: 132: 129: 126: 116: 104:{\textstyle x} 100: 63:Turing machine 15: 9: 6: 4: 3: 2: 16743: 16732: 16729: 16727: 16724: 16722: 16719: 16717: 16714: 16712: 16709: 16707: 16704: 16703: 16701: 16686: 16683: 16681: 16678: 16676: 16673: 16671: 16668: 16666: 16663: 16661: 16658: 16656: 16653: 16651: 16648: 16646: 16643: 16641: 16638: 16637: 16635: 16631: 16621: 16618: 16616: 16613: 16611: 16608: 16606: 16603: 16601: 16598: 16596: 16593: 16591: 16588: 16586: 16583: 16581: 16578: 16576: 16573: 16571: 16568: 16566: 16563: 16561: 16558: 16556: 16553: 16551: 16548: 16546: 16543: 16541: 16538: 16536: 16533: 16531: 16528: 16526: 16523: 16522: 16520: 16516: 16510: 16507: 16505: 16502: 16500: 16497: 16495: 16492: 16490: 16487: 16485: 16482: 16480: 16477: 16475: 16472: 16470: 16467: 16465: 16462: 16460: 16457: 16455: 16452: 16450: 16447: 16445: 16442: 16440: 16437: 16435: 16432: 16430: 16427: 16426: 16424: 16420: 16417: 16413: 16403: 16400: 16398: 16395: 16393: 16390: 16388: 16385: 16383: 16380: 16378: 16375: 16373: 16370: 16368: 16365: 16363: 16360: 16358: 16355: 16353: 16350: 16348: 16345: 16343: 16342:Performatives 16340: 16338: 16335: 16333: 16330: 16328: 16325: 16323: 16322:Logophoricity 16320: 16318: 16315: 16313: 16310: 16308: 16305: 16303: 16300: 16298: 16295: 16293: 16290: 16288: 16285: 16283: 16280: 16278: 16275: 16273: 16270: 16268: 16265: 16263: 16260: 16258: 16255: 16253: 16250: 16248: 16245: 16243: 16240: 16238: 16235: 16233: 16230: 16228: 16225: 16223: 16220: 16218: 16215: 16214: 16212: 16208: 16202: 16199: 16197: 16194: 16192: 16189: 16187: 16184: 16182: 16179: 16177: 16174: 16172: 16169: 16167: 16164: 16162: 16159: 16157: 16156:Evidentiality 16154: 16152: 16149: 16147: 16144: 16142: 16139: 16137: 16134: 16132: 16129: 16127: 16124: 16123: 16121: 16117: 16114: 16110: 16104: 16101: 16099: 16096: 16094: 16091: 16089: 16086: 16084: 16081: 16079: 16076: 16074: 16071: 16069: 16066: 16064: 16061: 16059: 16056: 16054: 16051: 16049: 16046: 16044: 16041: 16039: 16036: 16035: 16033: 16029: 16025: 16018: 16013: 16011: 16006: 16004: 15999: 15998: 15995: 15985: 15984: 15979: 15971: 15965: 15962: 15960: 15957: 15955: 15952: 15950: 15947: 15943: 15940: 15939: 15938: 15935: 15933: 15930: 15928: 15925: 15923: 15919: 15916: 15914: 15911: 15909: 15906: 15904: 15901: 15899: 15896: 15895: 15893: 15889: 15883: 15880: 15878: 15875: 15873: 15872:Recursive set 15870: 15868: 15865: 15863: 15860: 15858: 15855: 15853: 15850: 15846: 15843: 15841: 15838: 15836: 15833: 15831: 15828: 15826: 15823: 15822: 15821: 15818: 15816: 15813: 15811: 15808: 15806: 15803: 15801: 15798: 15796: 15793: 15792: 15790: 15788: 15784: 15778: 15775: 15773: 15770: 15768: 15765: 15763: 15760: 15758: 15755: 15753: 15750: 15748: 15745: 15741: 15738: 15736: 15733: 15731: 15728: 15727: 15726: 15723: 15721: 15718: 15716: 15713: 15711: 15708: 15706: 15703: 15701: 15698: 15694: 15691: 15690: 15689: 15686: 15682: 15681:of arithmetic 15679: 15678: 15677: 15674: 15670: 15667: 15665: 15662: 15660: 15657: 15655: 15652: 15650: 15647: 15646: 15645: 15642: 15638: 15635: 15633: 15630: 15629: 15628: 15625: 15624: 15622: 15620: 15616: 15610: 15607: 15605: 15602: 15600: 15597: 15595: 15592: 15589: 15588:from ZFC 15585: 15582: 15580: 15577: 15571: 15568: 15567: 15566: 15563: 15561: 15558: 15556: 15553: 15552: 15551: 15548: 15546: 15543: 15541: 15538: 15536: 15533: 15531: 15528: 15526: 15523: 15521: 15518: 15517: 15515: 15513: 15509: 15499: 15498: 15494: 15493: 15488: 15487:non-Euclidean 15485: 15481: 15478: 15476: 15473: 15471: 15470: 15466: 15465: 15463: 15460: 15459: 15457: 15453: 15449: 15446: 15444: 15441: 15440: 15439: 15435: 15431: 15428: 15427: 15426: 15422: 15418: 15415: 15413: 15410: 15408: 15405: 15403: 15400: 15398: 15395: 15393: 15390: 15389: 15387: 15383: 15382: 15380: 15375: 15369: 15364:Example  15361: 15353: 15348: 15347: 15346: 15343: 15341: 15338: 15334: 15331: 15329: 15326: 15324: 15321: 15319: 15316: 15315: 15314: 15311: 15309: 15306: 15304: 15301: 15299: 15296: 15292: 15289: 15287: 15284: 15283: 15282: 15279: 15275: 15272: 15270: 15267: 15265: 15262: 15260: 15257: 15256: 15255: 15252: 15250: 15247: 15243: 15240: 15238: 15235: 15233: 15230: 15229: 15228: 15225: 15221: 15218: 15216: 15213: 15211: 15208: 15206: 15203: 15201: 15198: 15196: 15193: 15192: 15191: 15188: 15186: 15183: 15181: 15178: 15176: 15173: 15169: 15166: 15164: 15161: 15159: 15156: 15154: 15151: 15150: 15149: 15146: 15144: 15141: 15139: 15136: 15134: 15131: 15127: 15124: 15122: 15121:by definition 15119: 15118: 15117: 15114: 15110: 15107: 15106: 15105: 15102: 15100: 15097: 15095: 15092: 15090: 15087: 15085: 15082: 15081: 15078: 15075: 15073: 15069: 15064: 15058: 15054: 15044: 15041: 15039: 15036: 15034: 15031: 15029: 15026: 15024: 15021: 15019: 15016: 15014: 15011: 15009: 15008:Kripke–Platek 15006: 15004: 15001: 14997: 14994: 14992: 14989: 14988: 14987: 14984: 14983: 14981: 14977: 14969: 14966: 14965: 14964: 14961: 14959: 14956: 14952: 14949: 14948: 14947: 14944: 14942: 14939: 14937: 14934: 14932: 14929: 14927: 14924: 14921: 14917: 14913: 14910: 14906: 14903: 14901: 14898: 14896: 14893: 14892: 14891: 14887: 14884: 14883: 14881: 14879: 14875: 14871: 14863: 14860: 14858: 14855: 14853: 14852:constructible 14850: 14849: 14848: 14845: 14843: 14840: 14838: 14835: 14833: 14830: 14828: 14825: 14823: 14820: 14818: 14815: 14813: 14810: 14808: 14805: 14803: 14800: 14798: 14795: 14793: 14790: 14788: 14785: 14784: 14782: 14780: 14775: 14767: 14764: 14762: 14759: 14757: 14754: 14752: 14749: 14747: 14744: 14742: 14739: 14738: 14736: 14732: 14729: 14727: 14724: 14723: 14722: 14719: 14717: 14714: 14712: 14709: 14707: 14704: 14702: 14698: 14694: 14692: 14689: 14685: 14682: 14681: 14680: 14677: 14676: 14673: 14670: 14668: 14664: 14654: 14651: 14649: 14646: 14644: 14641: 14639: 14636: 14634: 14631: 14629: 14626: 14622: 14619: 14618: 14617: 14614: 14610: 14605: 14604: 14603: 14600: 14599: 14597: 14595: 14591: 14583: 14580: 14578: 14575: 14573: 14570: 14569: 14568: 14565: 14563: 14560: 14558: 14555: 14553: 14550: 14548: 14545: 14543: 14540: 14538: 14535: 14534: 14532: 14530: 14529:Propositional 14526: 14520: 14517: 14515: 14512: 14510: 14507: 14505: 14502: 14500: 14497: 14495: 14492: 14488: 14485: 14484: 14483: 14480: 14478: 14475: 14473: 14470: 14468: 14465: 14463: 14460: 14458: 14457:Logical truth 14455: 14453: 14450: 14449: 14447: 14445: 14441: 14438: 14436: 14432: 14426: 14423: 14421: 14418: 14416: 14413: 14411: 14408: 14406: 14403: 14401: 14397: 14393: 14389: 14387: 14384: 14382: 14379: 14377: 14373: 14370: 14369: 14367: 14365: 14359: 14354: 14348: 14345: 14343: 14340: 14338: 14335: 14333: 14330: 14328: 14325: 14323: 14320: 14318: 14315: 14313: 14310: 14308: 14305: 14303: 14300: 14298: 14295: 14293: 14290: 14286: 14283: 14282: 14281: 14278: 14277: 14275: 14271: 14267: 14260: 14255: 14253: 14248: 14246: 14241: 14240: 14237: 14225: 14222: 14220: 14217: 14216: 14214: 14210: 14204: 14201: 14199: 14196: 14195: 14193: 14189: 14183: 14180: 14178: 14175: 14173: 14170: 14168: 14165: 14163: 14160: 14158: 14155: 14153: 14150: 14148: 14145: 14143: 14140: 14138: 14135: 14133: 14130: 14128: 14125: 14123: 14120: 14118: 14117:Alfred Foster 14115: 14113: 14110: 14108: 14105: 14103: 14102:William Boone 14100: 14098: 14095: 14093: 14092:Peter Andrews 14090: 14088: 14085: 14083: 14080: 14079: 14077: 14073: 14067: 14064: 14062: 14059: 14055: 14052: 14050: 14047: 14045: 14042: 14041: 14040: 14037: 14036: 14034: 14032:Notable ideas 14030: 14026: 14025:Alonzo Church 14019: 14014: 14012: 14007: 14005: 14000: 13999: 13996: 13990: 13989: 13984: 13982: 13981: 13976: 13972: 13970: 13969:C++ Templates 13966: 13963: 13960: 13956: 13954: 13951: 13948: 13945: 13943: 13939: 13936: 13932: 13931: 13927: 13924: 13920: 13918: 13917: 13913:Bret Victor, 13912: 13910: 13909: 13904: 13902: 13901: 13896: 13894: 13893: 13888: 13884: 13880: 13879: 13874: 13870: 13868: 13867: 13862: 13859: 13855: 13854: 13835: 13831: 13827: 13821: 13806: 13802: 13798: 13794: 13787: 13780: 13772: 13768: 13763: 13758: 13755:(2): 89–101. 13754: 13750: 13746: 13742: 13741:Landin, P. J. 13736: 13727: 13722: 13715: 13713: 13703: 13698: 13694: 13690: 13686: 13679: 13677: 13668: 13664: 13660: 13658:9781450328869 13654: 13650: 13646: 13641: 13636: 13632: 13625: 13617: 13613: 13609: 13605: 13598: 13591: 13583: 13581:9783540543961 13577: 13573: 13569: 13564: 13559: 13555: 13551: 13544: 13528: 13523: 13519: 13515: 13508: 13501: 13486: 13480: 13476: 13472: 13468: 13461: 13454: 13446: 13444:0-262-16209-1 13440: 13436: 13432: 13431: 13426: 13420: 13411: 13396: 13392: 13388: 13384: 13380: 13376: 13369: 13362: 13347: 13341: 13337: 13333: 13329: 13325: 13321: 13314: 13307: 13288: 13281: 13274: 13270: 13264: 13262: 13253:on 2009-02-05 13249: 13242: 13241: 13233: 13227: 13221: 13214: 13208: 13204: 13197: 13189: 13185: 13181: 13177: 13173: 13167: 13160: 13156: 13151: 13146: 13139: 13138: 13130: 13128: 13120: 13115: 13111: 13105: 13090: 13084: 13082: 13074: 13068: 13066:0-444-87508-5 13062: 13058: 13057: 13052: 13046: 13039: 13035: 13031: 13028:Dana Scott, " 13025: 13009: 13005: 12998: 12983: 12981:9789027722454 12977: 12973: 12972: 12967: 12960: 12952: 12948: 12944: 12940: 12936: 12932: 12928: 12924: 12920: 12914: 12906: 12902: 12898: 12894: 12890: 12886: 12882: 12876: 12874: 12865: 12861: 12857: 12853: 12849: 12845: 12841: 12837: 12831: 12823: 12819: 12815: 12811: 12807: 12803: 12799: 12798:Rosser, J. B. 12795: 12789: 12781: 12777: 12773: 12769: 12765: 12761: 12757: 12751: 12744:. p. 53. 12743: 12740: 12734: 12726: 12722: 12721: 12713: 12704: 12698: 12694: 12693: 12688: 12682: 12674: 12668: 12664: 12663: 12655: 12647: 12645:9789067653879 12641: 12637: 12636: 12628: 12612: 12608: 12607:"Type Theory" 12604: 12598: 12590: 12586: 12582: 12578: 12574: 12570: 12566: 12562: 12558: 12552: 12546: 12544: 12539: 12534: 12524: 12523: 12518: 12512: 12510: 12508: 12503: 12501: 12500: 12498: 12494: 12477: 12469: 12463: 12456: 12450: 12445: 12438: 12420: 12400: 12390: 12383: 12377: 12371: 12365: 12346: 12340: 12317: 12314: 12311: 12308: 12295: 12277: 12274: 12271: 12268: 12260: 12241: 12238: 12235: 12232: 12220: 12214: 12212: 12194: 12190: 12187: 12184: 12181: 12178: 12175: 12172: 12169: 12166: 12163: 12153: 12146: 12121: 12119: 12109: 12100: 12097: 12096: 12092: 12090: 12088: 12086: 12060: 12054: 12042: 12036: 12033: 12030: 12027: 12015: 12009: 12006: 12003: 12000: 11994: 11991: 11988: 11982: 11979: 11976: 11973: 11970: 11967: 11954: 11950: 11939: 11935: 11934:Church–Rosser 11931: 11927: 11923: 11922: 11918: 11915: 11914: 11910: 11907: 11903: 11902: 11898: 11895: 11891: 11890: 11886: 11883: 11879: 11878: 11874: 11871: 11867: 11866: 11862: 11861: 11857: 11856: 11851: 11849:0-262-16209-1 11845: 11842:, MIT Press, 11841: 11836: 11833: 11829: 11825: 11821: 11817: 11816:0-444-52077-5 11813: 11809: 11805: 11804: 11801: 11798: 11797: 11794: 11790: 11787: 11783: 11777: 11773: 11769: 11765: 11761: 11757: 11756: 11755:Studia Logica 11751: 11747: 11744: 11743: 11738: 11734: 11728: 11724: 11719: 11716: 11715: 11711:Larson, Jim, 11710: 11707: 11703: 11699: 11695: 11694:Landin, Peter 11692: 11689: 11685: 11681: 11676: 11671: 11667: 11663: 11656: 11654: 11648: 11644: 11641: 11637: 11624: 11623: 11617: 11614: 11610: 11606: 11603: 11599: 11595: 11592: 11588: 11586: 11585:0-7204-2285-X 11582: 11578: 11577:North-Holland 11574: 11570: 11566: 11563: 11559: 11556: 11555: 11551: 11548: 11545: 11544:0-262-51087-1 11541: 11537: 11536:The MIT Press 11533: 11529: 11528: 11518: 11514: 11511: 11508: 11505: 11503: 11499: 11498: 11494: 11491: 11488: 11485: 11481: 11478: 11475: 11472: 11470: 11467: 11464: 11461: 11458: 11455: 11452: 11449: 11447: 11444: 11440: 11437: 11434: 11431: 11429: 11426: 11423: 11420: 11418: 11415: 11413: 11409: 11406: 11404: 11400: 11397: 11394: 11390: 11386: 11385:Domain theory 11383: 11380: 11377: 11374: 11371: 11369: 11365: 11362: 11359: 11356: 11353: 11349: 11346: 11344: 11340: 11337: 11334: 11330: 11327: 11326: 11321: 11315: 11310: 11300: 11299: 11294: 11293: 11288: 11287: 11282: 11279: 11276: 11273: 11272: 11271: 11265: 11262: 11261: 11260: 11255: 11251: 11248: 11245: 11242: 11241: 11240: 11238: 11230: 11226: 11223: 11220: 11217: 11214: 11211: 11210: 11209: 11207: 11197: 11195: 11190: 11188: 11184: 11181: 11177: 11173: 11168: 11166: 11165:singleton set 11162: 11158: 11154: 11150: 11146: 11142: 11138: 11134: 11130: 11119: 11117: 11113: 11109: 11105: 11102: 11098: 11094: 11093:Church–Rosser 11084: 11082: 11078: 11074: 11070: 11066: 11062: 11058: 11054: 11050: 11046: 11042: 11038: 11035:For example, 11033: 10990: 10988: 10982: 10972: 10970: 10966: 10956: 10954: 10950: 10945: 10940: 10938: 10934: 10929: 10927: 10923: 10918: 10913: 10909: 10907: 10903: 10897: 10891: 10885: 10879: 10873: 10863: 10860: 10855: 10850: 10845: 10841: 10836: 10834: 10826: 10822: 10818: 10813: 10807: 10801: 10791: 10787: 10783: 10779: 10775: 10771: 10767: 10763: 10759: 10755: 10751: 10747: 10743: 10739: 10735: 10731: 10727: 10712:Computability 10705: 10702: 10699: 10696: 10695: 10694: 10687: 10683: 10679: 10672: 10668: 10664: 10660: 10654: 10651: 10647: 10645:Call by value 10644: 10643: 10642: 10636: 10633: 10618: 10588: 10585: 10579: 10576: 10573: 10566: 10563: 10557: 10554: 10551: 10543: 10540: 10537: 10534: 10521: 10518: 10514: 10511: 10510: 10509: 10504: 10494: 10492: 10488: 10484: 10480: 10476: 10472: 10467: 10465: 10461: 10457: 10453: 10449: 10445: 10440: 10438: 10434: 10418: 10410: 10406: 10400: 10390: 10388: 10384: 10380: 10376: 10372: 10368: 10363: 10358: 10354: 10350: 10346: 10342: 10338: 10333: 10331: 10327: 10322: 10314: 10309: 10303: 10299: 10295: 10289: 10284: 10278: 10274: 10270: 10266: 10262: 10258: 10253: 10248: 10240: 10235: 10230: 10226: 10221: 10216: 10213: 10209: 10206: 10201: 10196: 10193: 10190: 10185: 10180: 10177: 10173: 10168: 10163: 10160: 10158: 10153: 10147: 10142: 10139: 10138: 10137: 10135: 10130: 10125: 10121: 10116: 10111: 10106: 10101: 10097: 10092: 10086: 10081: 10076: 10072: 10068: 10062: 10052: 10049: 10043: 10038: 10024: 10020: 10014: 10010: 10005: 10000: 9994: 9988: 9982: 9977: 9973: 9968: 9962: 9956: 9948: 9944: 9940: 9937: 9934: 9930: 9926: 9922: 9918: 9914: 9911: 9908: 9905: 9901: 9897: 9893: 9889: 9886: 9883: 9880: 9876: 9872: 9868: 9864: 9860: 9856: 9853: 9849: 9845: 9841: 9837: 9833: 9829: 9826: 9822: 9818: 9814: 9810: 9806: 9803: 9799: 9796: 9792: 9788: 9784: 9780: 9776: 9773: 9769: 9765: 9761: 9760: 9759: 9751: 9748: 9737: 9732: 9729:G) (0−1)))))) 9728: 9723: 9719: 9715: 9711: 9707: 9703: 9698: 9694: 9689: 9685: 9680: 9676: 9672: 9668: 9664: 9660: 9655: 9651: 9646: 9642: 9637: 9633: 9629: 9625: 9621: 9617: 9612: 9608: 9605:4 × (3 × (G ( 9603: 9599: 9594: 9591:−1)))) (4−1)) 9590: 9586: 9582: 9578: 9574: 9569: 9565: 9560: 9556: 9551: 9547: 9543: 9539: 9535: 9531: 9526: 9522: 9518: 9514: 9510: 9506: 9502: 9498: 9493: 9489: 9484: 9480: 9475: 9474: 9473: 9471: 9467: 9462: 9458: 9447: 9444: 9440: 9436: 9432: 9429: 9425: 9421: 9417: 9414: 9410: 9406: 9402: 9398: 9394: 9391: 9387: 9383: 9379: 9376: 9372: 9368: 9363: 9360: 9356: 9353: 9349: 9345: 9341: 9338: 9334: 9330: 9326: 9321: 9318: 9315: 9311: 9310: 9309: 9306: 9300: 9297: 9287: 9284: 9280: 9276: 9272: 9269: 9265: 9261: 9257: 9253: 9249: 9248: 9247: 9240: 9238: 9222: 9205: 9201: 9197: 9193: 9187: 9186: 9185: 9184: 9181: 9177: 9173: 9170: 9166: 9162: 9158: 9149: 9140: 9136: 9130: 9127: 9123: 9119: 9116: 9111: 9110: 9109: 9108: 9105: 9101: 9097: 9093: 9089: 9085: 9080: 9079: 9078: 9075: 9068: 9065: 9061: 9056: 9047: 9041: 9038: 9034: 9030: 9027: 9024: 9019: 9018: 9017: 9016: 9013: 9009: 9006: 9002: 8998: 8994: 8990: 8985: 8984: 8983: 8980: 8975: 8965: 8961: 8957: 8953: 8948: 8947: 8946: 8942: 8936: 8933:Consider the 8931: 8929: 8924: 8920: 8917: 8913: 8907: 8902: 8897: 8891: 8881: 8871: 8866: 8861: 8857: 8852: 8842: 8836: 8830: 8825: 8820: 8819: 8818: 8812: 8805: 8799: 8794: 8789: 8788: 8787: 8785: 8781: 8776: 8770: 8760: 8758: 8754: 8750: 8736: 8732: 8727: 8726: 8725: 8718: 8714: 8710: 8705: 8704: 8703: 8699: 8695: 8687: 8683: 8676: 8672: 8668: 8664: 8660: 8656: 8652: 8626: 8622: 8618: 8614: 8609: 8605: 8602:NIL := λ 8600: 8596: 8592: 8587: 8583: 8579: 8574: 8571: 8568: 8565: 8561: 8557: 8553: 8548: 8547: 8546: 8535: 8529: 8520: 8502: 8499: 8493: 8486: 8482: 8479: 8475: 8471: 8467: 8463: 8459: 8449: 8445: 8442: 8438: 8434: 8430: 8426: 8422: 8418: 8413: 8412: 8411: 8400: 8397: 8394: 8387: 8384: 8377: 8373: 8362: 8359: 8356:.ISZERO (SUB 8355: 8351: 8348:LEQ := λ 8346: 8345: 8344: 8337: 8333: 8329: 8324: 8323: 8322: 8304: 8299: 8278: 8274: 8270: 8265: 8257: 8254: 8251: 8247: 8243: 8238: 8237: 8233: 8232: 8231: 8225: 8222: 8219: 8215: 8211: 8207: 8202: 8198: 8194: 8191:NOT := λ 8189: 8186: 8183: 8180: 8176: 8172: 8167: 8164: 8161: 8158: 8154: 8150: 8147:AND := λ 8145: 8144: 8143: 8137: 8133: 8129: 8124: 8121: 8117: 8113: 8108: 8107: 8106: 8090: 8083: 8079: 8073: 8069: 8063: 8060: 8050: 8046: 8042: 8038: 8035:SUB := λ 8033: 8032: 8031: 8029: 8025: 8015: 8008: 8004: 8000: 7996: 7992: 7988: 7980: 7977: 7973: 7969: 7965: 7959: 7950: 7946: 7942: 7938: 7934: 7931: 7927: 7923: 7919: 7915: 7911: 7907: 7903: 7898: 7897: 7896: 7889: 7882: 7878: 7868: 7865: 7861: 7857: 7854:POW := λ 7852: 7851: 7850: 7847: 7841: 7835: 7829: 7819: 7815: 7811: 7807: 7802: 7801: 7800: 7793: 7790: 7786: 7782: 7778: 7774: 7769: 7768: 7767: 7761: 7757: 7753: 7749: 7744: 7743: 7742: 7739: 7733: 7727: 7716: 7715: 7714: 7706: 7705: 7704: 7694: 7691: 7688: 7684: 7681: 7677: 7673: 7669: 7665: 7660: 7659: 7658: 7655: 7649: 7645: 7639: 7633: 7627: 7621: 7611: 7608: 7605: 7601: 7597: 7593: 7589: 7584: 7583: 7582: 7579: 7572: 7566: 7560: 7553: 7549: 7545: 7541: 7536: 7535: 7534: 7532: 7528: 7524: 7520: 7508: 7503: 7497: 7496:impossible.) 7491: 7486: 7480: 7474: 7470:-th power of 7468: 7462: 7456: 7450: 7444: 7438: 7432: 7426: 7420: 7415: 7406: 7403: 7399: 7395: 7391: 7386: 7382: 7379: 7375: 7371: 7366: 7363: 7360: 7356: 7351: 7348: 7344: 7339: 7338: 7337: 7335: 7334: 7324: 7321: 7317: 7313: 7309: 7305: 7300: 7296: 7293: 7289: 7285: 7281: 7276: 7273: 7270: 7266: 7262: 7257: 7254: 7250: 7246: 7241: 7240: 7239: 7237: 7233: 7223: 7221: 7220: 7215: 7214: 7209: 7208: 7203: 7202: 7197: 7191: 7187: 7177: 7173: 7171: 7166: 7164: 7160: 7156: 7150: 7140: 7138: 7134: 7130: 7125: 7123: 7119: 7115: 7111: 7108: 7104: 7100: 7096: 7092: 7088: 7079: 7077: 7073: 7069: 7064: 7062: 7058: 7053: 7051: 7047: 7043: 7039: 7035: 7031: 7022: 7021: 7020: 7014: 7010: 7006: 7002: 6998: 6994: 6990: 6986: 6979: 6978: 6972: 6968: 6964: 6960: 6956: 6952: 6948: 6944: 6940: 6938: 6934: 6930: 6926: 6922: 6917: 6911: 6904: 6898: 6894: 6892: 6888: 6884: 6880: 6877: 6875: 6871: 6868: 6867: 6866: 6864: 6860: 6856: 6852: 6848: 6838: 6836: 6831: 6829: 6825: 6821: 6817: 6812: 6810: 6806: 6802: 6798: 6794: 6790: 6786: 6782: 6777: 6775: 6771: 6767: 6763: 6759: 6755: 6751: 6747: 6743: 6739: 6735: 6729: 6727: 6723: 6719: 6716:might yield λ 6715: 6711: 6707: 6703: 6694: 6692: 6688: 6684: 6680: 6676: 6671: 6669: 6665: 6661: 6657: 6653: 6649: 6645: 6641: 6637: 6633: 6629: 6625: 6621: 6616: 6614: 6606: 6603: 6600: 6597: 6594: 6591: 6590: 6589: 6586: 6578: 6576: 6572: 6568: 6559: 6555: 6551: 6546: 6543: 6539: 6535: 6531: 6527: 6524: 6520: 6516: 6512: 6511: 6510: 6508: 6504: 6500: 6495: 6493: 6489: 6485: 6481: 6477: 6473: 6469: 6465: 6461: 6457: 6453: 6449: 6445: 6441: 6437: 6433: 6429: 6425: 6412: 6408: 6404: 6400: 6396: 6392: 6388: 6385: 6381: 6377: 6373: 6369: 6365: 6361: 6357: 6353: 6350: 6347: 6344: 6340: 6336: 6333: 6329: 6326: 6322: 6319: 6316: 6312: 6309: 6306: 6302: 6299: 6295: 6294: 6293: 6174: 6172: 6167: 6166: 6165: 6159: 6155: 6146: 6138: 6134: 6129: 6125: 6121: 6113: 6108: 6104: 6100: 6095: 6091: 6090: 6089: 6087: 6075: 6072: 6066: 6059: 6055: 6054: 6053: 6044: 6034: 6032: 6026: 6009: 6006: 6003: 6000: 5997: 5988: 5985: 5982: 5979: 5976: 5970: 5961: 5958: 5955: 5952: 5949: 5946: 5943: 5937: 5925: 5922: 5919: 5916: 5913: 5910: 5907: 5901: 5895: 5889: 5886: 5883: 5880: 5877: 5874: 5871: 5862: 5859: 5847: 5844: 5841: 5838: 5835: 5826: 5823: 5820: 5817: 5814: 5788: 5785: 5782: 5779: 5776: 5767: 5764: 5761: 5758: 5755: 5749: 5738: 5734: 5729: 5715: 5712: 5709: 5706: 5686: 5683: 5677: 5674: 5671: 5665: 5659: 5653: 5650: 5647: 5644: 5621: 5618: 5615: 5612: 5592: 5589: 5583: 5580: 5577: 5571: 5565: 5559: 5556: 5553: 5550: 5527: 5504: 5501: 5498: 5492: 5485:β-reduces to 5472: 5466: 5463: 5460: 5457: 5431: 5428: 5425: 5419: 5413: 5407: 5404: 5401: 5398: 5372: 5369: 5366: 5360: 5340: 5334: 5331: 5328: 5325: 5308: 5294: 5291: 5288: 5285: 5282: 5273: 5270: 5267: 5261: 5255: 5252: 5249: 5246: 5240: 5237: 5234: 5225: 5222: 5219: 5216: 5193: 5170: 5167: 5164: 5155: 5152: 5149: 5146: 5134: 5120: 5117: 5114: 5111: 5091: 5088: 5085: 5082: 5062: 5059: 5056: 5053: 5050: 5041: 5038: 5035: 5029: 5023: 5020: 5017: 5014: 5008: 5005: 5002: 4993: 4990: 4987: 4984: 4972: 4958: 4950: 4934: 4925: 4911: 4905: 4902: 4899: 4896: 4890: 4881: 4878: 4875: 4869: 4857: 4854: 4851: 4842: 4839: 4836: 4833: 4824: 4818: 4815: 4812: 4803: 4797: 4794: 4791: 4788: 4762: 4759: 4756: 4753: 4750: 4741: 4738: 4735: 4729: 4723: 4720: 4717: 4714: 4708: 4705: 4702: 4693: 4690: 4687: 4684: 4674:For example, 4657: 4637: 4617: 4609: 4593: 4573: 4553: 4533: 4530: 4527: 4501: 4498: 4495: 4489: 4483: 4480: 4477: 4474: 4468: 4465: 4462: 4453: 4450: 4447: 4444: 4434: 4419: 4416: 4413: 4410: 4407: 4401: 4398: 4395: 4386: 4383: 4380: 4377: 4367: 4346: 4343: 4340: 4334: 4322: 4319: 4316: 4310: 4304: 4298: 4295: 4292: 4283: 4264: 4254: 4240: 4220: 4200: 4180: 4160: 4153: ; with 4140: 4137: 4134: 4114: 4111: 4105: 4102: 4099: 4093: 4086: 4072: 4052: 4032: 4012: 4005: ; with 3992: 3989: 3983: 3980: 3977: 3971: 3964: 3963: 3962: 3960: 3944: 3924: 3904: 3881: 3878: 3875: 3869: 3849: 3829: 3809: 3789: 3769: 3755: 3741: 3721: 3702: 3699: 3696: 3693: 3673: 3670: 3667: 3664: 3640: 3620: 3600: 3581: 3573: 3569: 3554: 3534: 3514: 3511: 3508: 3505: 3497: 3493: 3479: 3459: 3451: 3450: 3449: 3447: 3437: 3434: 3420: 3400: 3380: 3377: 3374: 3371: 3351: 3348: 3345: 3342: 3334: 3324: 3321: 3301: 3298: 3292: 3286: 3283: 3280: 3277: 3274: 3271: 3268: 3265: 3262: 3254: 3238: 3218: 3212: 3205: 3189: 3186: 3183: 3180: 3160: 3154: 3146: 3130: 3127: 3124: 3121: 3112: 3110: 3100: 3086: 3083: 3080: 3077: 3070: 3054: 3034: 3008: 3005: 3002: 2999: 2993: 2990: 2987: 2964: 2944: 2924: 2904: 2897:, with input 2881: 2878: 2875: 2872: 2849: 2843: 2840: 2837: 2834: 2811: 2791: 2788: 2785: 2782: 2774: 2771: 2766: 2743: 2723: 2703: 2678: 2675: 2672: 2669: 2663: 2660: 2657: 2647: 2632: 2629: 2626: 2623: 2600: 2594: 2591: 2588: 2585: 2576: 2573: 2570: 2563: 2562: 2561: 2558: 2537: 2534: 2531: 2525: 2522: 2519: 2495: 2492: 2489: 2486: 2480: 2474: 2451: 2448: 2445: 2439: 2436: 2433: 2424: 2407: 2401: 2365: 2345: 2338: 2333: 2324:the variable 2323: 2305: 2302: 2299: 2296: 2273: 2249: 2246: 2241: 2237: 2216: 2213: 2210: 2205: 2201: 2197: 2191: 2185: 2165: 2142: 2139: 2134: 2130: 2123: 2120: 2117: 2101: 2085: 2082: 2079: 2076: 2069: 2064: 2050: 2045: 2041: 2037: 2034: 2031: 2023: 2014: 1995: 1975: 1956: 1953: 1934: 1931: 1928: 1925: 1906: 1899: 1898: 1897: 1895: 1890: 1888: 1884: 1874: 1872: 1867: 1865: 1861: 1857: 1847: 1830: 1827: 1820: 1805: 1785: 1763: 1759: 1755: 1750: 1746: 1742: 1735: 1720: 1700: 1677: 1666: 1662: 1658: 1653: 1649: 1642: 1636: 1629: 1612: 1596: 1578: 1574: 1570: 1565: 1561: 1554: 1545: 1524: 1523: 1522: 1504: 1501: 1494: 1478: 1474: 1470: 1465: 1461: 1457: 1450: 1433: 1430: 1427: 1416: 1412: 1408: 1403: 1399: 1389: 1386: 1383: 1370: 1369: 1368: 1317: 1313: 1311: 1287: 1283: 1279: 1274: 1270: 1263: 1254: 1247: 1246: 1245: 1226: 1222: 1218: 1213: 1209: 1199: 1196: 1193: 1183: 1182: 1181: 1179: 1125: 1108: 1102: 1095: 1094: 1093: 1076: 1073: 1067: 1061: 1058: 1051: 1050: 1049: 1033: 1029: 1025: 1020: 1016: 1007: 995: 974: 970: 966: 961: 957: 947: 944: 941: 931: 930: 929: 927: 906: 902: 898: 893: 889: 885: 879: 876: 873: 867: 828: 827: 826: 823: 819: 805: 803: 797: 795: 791: 790:iota operator 786: 782: 779: 774: 771: 757: 737: 734: 708: 697: 675: 662: 660: 652: 646: 644: 639: 637: 631: 629: 625: 621: 618:in 1935 when 617: 613: 609: 608:Alonzo Church 599: 597: 593: 589: 585: 581: 577: 573: 568: 566: 562: 558: 554: 550: 546: 541: 539: 535: 531: 527: 523: 513: 511: 506: 504: 503:β-normal form 500: 496: 492: 484: 483:: β-reduction 463: 460: 457: 451: 439: 430: 427: 424: 421: 408: 405: 401: 380: 374: 371: 368: 365: 350: 344: 341: 338: 335: 325: 324: 323: 305: 285: 265: 245: 237: 218: 212: 202: 187: 179: 163: 155: 136: 133: 130: 127: 117: 114: 98: 91: 90: 89: 87: 83: 78: 76: 72: 68: 67:Alonzo Church 64: 60: 56: 52: 48: 44: 40: 36: 32: 31:formal system 28: 26: 21: 16615:Type shifter 16585:Quantization 16535:Continuation 16473: 16402:Veridicality 16282:Exhaustivity 16247:Cumulativity 16166:Indexicality 16146:Definiteness 16141:Conditionals 16068:Logical form 15974: 15856: 15772:Ultraproduct 15619:Model theory 15584:Independence 15520:Formal proof 15512:Proof theory 15495: 15468: 15425:real numbers 15397:second-order 15308:Substitution 15185:Metalanguage 15126:conservative 15099:Axiom schema 15043:Constructive 15013:Morse–Kelley 14979:Set theories 14958:Aleph number 14951:inaccessible 14857:Grothendieck 14741:intersection 14628:Higher-order 14616:Second-order 14562:Truth tables 14519:Venn diagram 14302:Formal proof 14191:Institutions 14107:Martin Davis 14038: 13987: 13978: 13957:Mike Thyer, 13921: 13914: 13907: 13898: 13897:L. Allison, 13890: 13876: 13864: 13837:. Retrieved 13829: 13820: 13808:. Retrieved 13796: 13792: 13779: 13752: 13748: 13735: 13726:1701.04240v1 13692: 13688: 13630: 13624: 13607: 13603: 13590: 13553: 13543: 13531:. Retrieved 13517: 13513: 13500: 13488:. Retrieved 13466: 13453: 13429: 13419: 13410: 13398:. Retrieved 13378: 13374: 13361: 13349:. Retrieved 13319: 13306: 13294:. Retrieved 13280: 13268: 13248:the original 13239: 13232: 13224:Luke Palmer 13220: 13202: 13196: 13179: 13175: 13166: 13136: 13117: 13113: 13104: 13093:. Retrieved 13055: 13045: 13024: 13014:November 17, 13012:. Retrieved 13007: 12997: 12985:. Retrieved 12974:. Springer. 12970: 12959: 12929:(2): 56–68. 12926: 12922: 12913: 12888: 12884: 12847: 12843: 12839: 12830: 12805: 12801: 12788: 12763: 12762:. Series 2. 12759: 12750: 12741: 12733: 12725:the original 12719: 12712: 12691: 12681: 12665:. Springer. 12661: 12654: 12634: 12627: 12617:November 17, 12615:. Retrieved 12610: 12597: 12564: 12560: 12551: 12542: 12533: 12521: 12495:, used with 12490: 12489: 12467: 12462: 12454: 12448: 12443: 12437: 12389: 12381: 12376: 12364: 12294: 12219: 12208: 12152: 12108: 12098: 11953: 11932:(due to the 11920: 11912: 11899: 11887: 11875: 11863: 11839: 11810:, Elsevier, 11807: 11785: 11759: 11753: 11740: 11722: 11713: 11697: 11683: 11665: 11661: 11652: 11627:. Retrieved 11621: 11608: 11601: 11572: 11568: 11553: 11495: 11480:SECD machine 11296: 11290: 11284: 11269: 11258: 11234: 11203: 11191: 11182: 11169: 11160: 11156: 11152: 11148: 11140: 11136: 11132: 11128: 11125: 11096: 11090: 11075:("agents"), 11034: 11019: 10984: 10965:Peter Landin 10962: 10941: 10936: 10932: 10930: 10916: 10911: 10905: 10901: 10895: 10889: 10883: 10877: 10869: 10858: 10848: 10837: 10824: 10820: 10811: 10805: 10799: 10789: 10785: 10781: 10777: 10773: 10769: 10765: 10761: 10757: 10753: 10749: 10745: 10733: 10715: 10703:Call by need 10692: 10685: 10681: 10677: 10670: 10666: 10662: 10658: 10652:Call by name 10640: 10512:Normal order 10506: 10475:proof theory 10468: 10464:type systems 10441: 10436: 10404: 10402: 10378: 10374: 10370: 10366: 10361: 10356: 10352: 10348: 10344: 10340: 10336: 10334: 10329: 10325: 10320: 10318:would do if 10312: 10307: 10301: 10297: 10293: 10287: 10282: 10276: 10272: 10268: 10264: 10260: 10256: 10251: 10246: 10244: 10238: 10233: 10228: 10224: 10219: 10214: 10211: 10207: 10204: 10199: 10194: 10188: 10183: 10178: 10175: 10171: 10166: 10161: 10156: 10151: 10145: 10140: 10133: 10128: 10126:contains an 10123: 10119: 10114: 10109: 10104: 10099: 10095: 10090: 10084: 10079: 10074: 10066: 10064: 10047: 10041: 10022: 10018: 10012: 10008: 9998: 9992: 9986: 9980: 9966: 9960: 9954: 9952: 9946: 9942: 9935: 9932: 9928: 9924: 9920: 9916: 9909: 9906: 9903: 9899: 9895: 9891: 9884: 9881: 9878: 9874: 9870: 9866: 9862: 9854: 9851: 9847: 9843: 9839: 9835: 9831: 9824: 9820: 9816: 9812: 9804: 9801: 9797: 9794: 9790: 9786: 9782: 9778: 9771: 9767: 9763: 9757: 9746: 9743: 9726: 9717: 9713: 9709: 9705: 9701: 9695:G) (1−1))))) 9692: 9686:G) (1−1))))) 9683: 9674: 9670: 9666: 9662: 9658: 9649: 9640: 9631: 9627: 9623: 9619: 9615: 9614:4 × (3 × ((λ 9606: 9597: 9588: 9584: 9580: 9576: 9572: 9563: 9554: 9545: 9541: 9537: 9533: 9529: 9520: 9516: 9512: 9508: 9504: 9500: 9496: 9487: 9478: 9469: 9465: 9460: 9456: 9452: 9445: 9442: 9438: 9430: 9427: 9423: 9419: 9415: 9412: 9408: 9404: 9400: 9392: 9389: 9385: 9381: 9377: 9374: 9370: 9366: 9358: 9354: 9351: 9347: 9343: 9339: 9336: 9332: 9328: 9324: 9316: 9313: 9304: 9298: 9295: 9292: 9285: 9282: 9278: 9274: 9270: 9267: 9263: 9259: 9255: 9251: 9241: 9220: 9214: 9203: 9202:× ((FIX G) ( 9199: 9195: 9191: 9179: 9175: 9171: 9168: 9164: 9160: 9156: 9138: 9134: 9128: 9125: 9121: 9117: 9114: 9112:with  9103: 9099: 9095: 9091: 9087: 9083: 9076: 9073: 9066: 9063: 9059: 9045: 9039: 9036: 9032: 9028: 9025: 9022: 9020:with  9011: 9007: 9004: 9000: 8996: 8992: 8988: 8978: 8973: 8971: 8963: 8959: 8955: 8951: 8940: 8932: 8927: 8922: 8918: 8915: 8911: 8905: 8899: 8869: 8864: 8859: 8855: 8850: 8843: 8839: 8834: 8828: 8823: 8808: 8803: 8797: 8792: 8783: 8779: 8774: 8766: 8746: 8734: 8730: 8723: 8716: 8712: 8708: 8697: 8693: 8685: 8681: 8677: 8670: 8666: 8662: 8658: 8654: 8650: 8631: 8624: 8620: 8616: 8612: 8603: 8594: 8590: 8581: 8577: 8569: 8566: 8563: 8559: 8555: 8551: 8533: 8527: 8508: 8497: 8491: 8484: 8480: 8477: 8473: 8469: 8465: 8461: 8457: 8454: 8447: 8443: 8440: 8436: 8432: 8428: 8424: 8420: 8416: 8401: 8395: 8392: 8385: 8382: 8375: 8371: 8368: 8360: 8357: 8353: 8349: 8342: 8338:.FALSE) TRUE 8335: 8331: 8327: 8302: 8300: 8289: 8276: 8272: 8268: 8255: 8252: 8249: 8245: 8241: 8229: 8223: 8220: 8217: 8213: 8209: 8205: 8196: 8192: 8184: 8181: 8178: 8174: 8170: 8169:OR := λ 8162: 8159: 8156: 8152: 8148: 8141: 8135: 8131: 8127: 8119: 8115: 8111: 8096: 8081: 8077: 8071: 8067: 8061: 8058: 8055: 8048: 8044: 8040: 8036: 8024:conditionals 8013: 8006: 8002: 7998: 7994: 7990: 7986: 7978: 7975: 7971: 7967: 7963: 7957: 7955: 7948: 7944: 7940: 7936: 7932: 7929: 7925: 7921: 7917: 7913: 7909: 7905: 7901: 7887: 7880: 7876: 7872: 7866: 7863: 7859: 7855: 7845: 7839: 7833: 7827: 7824: 7817: 7813: 7809: 7805: 7798: 7791: 7788: 7784: 7780: 7776: 7772: 7765: 7759: 7755: 7751: 7747: 7737: 7731: 7729:to a number 7725: 7722: 7712: 7699: 7692: 7689: 7686: 7682: 7679: 7675: 7671: 7667: 7663: 7653: 7647: 7643: 7637: 7631: 7625: 7619: 7617:Because the 7616: 7609: 7606: 7603: 7599: 7595: 7591: 7587: 7577: 7570: 7568:and returns 7564: 7561: 7558: 7551: 7547: 7543: 7539: 7530: 7526: 7522: 7518: 7506: 7501: 7498: 7484: 7478: 7472: 7466: 7460: 7454: 7448: 7442: 7436: 7430: 7424: 7418: 7411: 7404: 7401: 7397: 7393: 7389: 7380: 7377: 7373: 7369: 7361: 7358: 7354: 7346: 7342: 7331: 7329: 7322: 7319: 7315: 7311: 7307: 7303: 7294: 7291: 7287: 7283: 7279: 7271: 7268: 7264: 7260: 7252: 7248: 7244: 7229: 7217: 7211: 7205: 7199: 7193: 7174: 7167: 7152: 7128: 7126: 7121: 7117: 7113: 7109: 7106: 7102: 7086: 7085: 7067: 7065: 7060: 7056: 7054: 7049: 7045: 7041: 7037: 7029: 7028: 7016: 7008: 7004: 7000: 6996: 6992: 6988: 6984: 6982: 6974: 6970: 6966: 6962: 6958: 6954: 6950: 6946: 6942: 6936: 6932: 6928: 6924: 6915: 6909: 6902: 6896: 6890: 6886: 6882: 6878: 6873: 6869: 6862: 6858: 6854: 6850: 6846: 6844: 6841:Substitution 6832: 6813: 6808: 6804: 6800: 6796: 6792: 6788: 6784: 6780: 6778: 6769: 6765: 6761: 6757: 6753: 6749: 6745: 6741: 6737: 6733: 6730: 6726:α-equivalent 6725: 6721: 6717: 6713: 6709: 6702:α-conversion 6701: 6700: 6697:α-conversion 6690: 6686: 6682: 6678: 6674: 6672: 6667: 6663: 6659: 6655: 6651: 6647: 6643: 6639: 6635: 6631: 6627: 6623: 6622:, short for 6619: 6617: 6613:α-equivalent 6612: 6610: 6604: 6598: 6593:α-conversion 6592: 6587: 6584: 6570: 6566: 6564: 6557: 6553: 6549: 6541: 6537: 6533: 6529: 6522: 6518: 6514: 6506: 6502: 6498: 6496: 6491: 6487: 6483: 6479: 6475: 6471: 6467: 6463: 6459: 6455: 6451: 6447: 6443: 6439: 6435: 6434:, the part λ 6431: 6427: 6423: 6421: 6410: 6406: 6402: 6398: 6394: 6390: 6383: 6379: 6375: 6374:) and not (λ 6371: 6367: 6363: 6359: 6348: 6345: 6342: 6338: 6331: 6327: 6324: 6320: 6317: 6314: 6307: 6304: 6303:instead of ( 6300: 6297: 6291: 6254: :== ( 6225: :== λ 6168: 6161: 6158:applications 6157: 6154:abstractions 6153: 6151: 6144: 6136: 6132: 6123: 6119: 6111: 6106: 6098: 6093: 6079: 6064: 6057: 6051: 6031:truth values 6027: 5730: 5314: 5206:, to obtain 5135: 4973: 4926: 4673: 3958: 3761: 3656: 3445: 3443: 3435: 3332: 3330: 3322: 3203: 3113: 3106: 2772: 2767: 2759: 2559: 2425: 2382:to an input 2336: 2334: 2328:in the term 2106:and returns 2067: 2065: 2018: 2012: 1951: 1891: 1886: 1880: 1877:Lambda terms 1868: 1856:lambda terms 1855: 1853: 1845: 1520: 1314: 1307: 1243: 1177: 1126: 1123: 1091: 991: 925: 923: 816: 799: 787: 784: 776: 772: 664: 656: 650: 640: 632: 624:J. B. Rosser 605: 569: 556: 552: 548: 544: 542: 519: 510:Iota and Jot 507: 488: 321: 177: 82:lambda terms 79: 55:substitution 24: 23: 19: 18: 16530:Context set 16504:Type theory 16387:Subtrigging 16151:Disjunction 16078:Proposition 15882:Type theory 15830:undecidable 15762:Truth value 15649:equivalence 15328:non-logical 14941:Enumeration 14931:Isomorphism 14878:cardinality 14862:Von Neumann 14827:Ultrafilter 14792:Uncountable 14726:equivalence 14643:Quantifiers 14633:Fixed-point 14602:First-order 14482:Consistency 14467:Proposition 14444:Traditional 14415:Lindström's 14405:Compactness 14347:Type theory 14292:Cardinality 14224:A. C. Croom 14147:Gary R. Mar 14122:Leon Henkin 14082:Alan Turing 13336:2318/149874 13292:. p. 6 13073:Corrections 11834:extensions. 11828:lambda cube 11412:β-reduction 11206:lambda cube 11145:cardinality 11108:parallelism 11053:first class 11041:subprograms 10840:normal form 10707:evaluation. 10407:is a typed 10071:combinators 9652:G) (2−1)))) 9643:G) (2−1)))) 9223:combinator 9221:fixed-point 9219:here), the 9082:G := λ 8987:G := λ 8707:Φ := λ 8489:is the add 8089:otherwise. 7488:) obey the 7388:3 := λ 7368:2 := λ 7353:1 := λ 7341:0 := λ 7302:3 := λ 7278:2 := λ 7259:1 := λ 7243:0 := λ 7157:is neither 7087:η-reduction 7082:η-reduction 7030:β-reduction 7025:β-reduction 6760:result in λ 6605:η-reduction 6599:β-reduction 6571:combinators 6497:The set of 6341:instead of 6249:application 6220:abstraction 6201:application 6191:abstraction 5737:Standard ML 5311:β-reduction 3547:, but with 3173:. Further, 2775:a function 2716:is of form 2616:is of form 2394:to produce 2337:application 2266:. The name 2178:defined by 2098:denotes an 2068:abstraction 2013:application 1952:abstraction 1887:lambda term 580:linguistics 572:mathematics 236:application 47:application 43:abstraction 39:computation 16700:Categories 16680:Pragmatics 16327:Mirativity 16093:Speech act 16048:Entailment 16043:Denotation 15693:elementary 15386:arithmetic 15254:Quantifier 15232:functional 15104:Expression 14822:Transitive 14766:identities 14751:complement 14684:hereditary 14667:Set theory 14172:Dana Scott 13839:6 November 13810:2022-12-01 13640:1601.01233 13400:14 January 13351:14 January 13296:14 January 13275:114 pages. 13176:Dialectica 13114:SoftOption 13095:2012-06-18 12808:(3): 630. 12497:permission 12486:References 11793:0954300653 11629:2020-04-14 11172:Dana Scott 11061:JavaScript 10949:Caml Light 10933:reasonable 10866:Complexity 10734:computable 10487:categories 10296:would do. 10210:) := 10174:) := 10155:) := 10016:, so that 9927: := λ 9894: := λ 9865: := λ 9834: := λ 9815: := λ 9781: := λ 9766: := λ 9708:= 0; else 9665:= 0; else 9622:= 0; else 9609:G) (3−1))) 9600:G) (3−1))) 9579:= 0; else 9536:= 0; else 9507:= 0; else 9254: := λ 9198:= 0; else 9159: := ( 9143: and 9094:= 0; else 9050: and 8999:= 0; else 8958:= 0; else 8954:) = 1, if 8894:See also: 8813:, such as 8669:_and_tail_ 8369:and since 8199:FALSE TRUE 7893:PRED 0 = 0 7641:gives the 7196:arithmetic 7135:, via the 7074:, via the 6799:, we get λ 6268:expression 6259:expression 6240:expression 6186: :== 6181:expression 6056:variables 6048:Definition 4233:) remains 2022:§ Notation 813:Motivation 778:Dana Scott 576:philosophy 16479:Mereology 16415:Formalism 16297:Givenness 16222:Cataphora 16210:Phenomena 16201:Vagueness 16131:Ambiguity 16083:Reference 16063:Intension 16053:Extension 15964:Supertask 15867:Recursion 15825:decidable 15659:saturated 15637:of models 15560:deductive 15555:axiomatic 15475:Hilbert's 15462:Euclidean 15443:canonical 15366:axiomatic 15298:Signature 15227:Predicate 15116:Extension 15038:Ackermann 14963:Operation 14842:Universal 14832:Recursive 14807:Singleton 14802:Inhabited 14787:Countable 14777:Types of 14761:power set 14731:partition 14648:Predicate 14594:Predicate 14509:Syllogism 14499:Soundness 14472:Inference 14462:Tautology 14364:paradoxes 13883:EMS Press 13695:: 23–43. 13558:CiteSeerX 13533:22 August 13490:22 August 13435:MIT Press 13150:0804.3434 12384:} removed 12344:↦ 12309:λ 12233:λ 12188:∣ 12176:λ 12173:∣ 12131:↦ 12028:λ 12001:λ 11989:λ 11977:λ 11968:λ 11858:Documents 11832:subtyping 11651:"Review: 11474:Rewriting 11159:, unless 11122:Semantics 11097:any order 11057:Smalltalk 11045:arguments 10574:λ 10552:λ 10535:λ 10419:λ 10409:formalism 9945: := 9566:G) (4−1)) 9557:G) (4−1)) 8974:parameter 8937:function 8935:factorial 8901:Recursion 8468:.ISZERO ( 8431:.ISZERO ( 8303:predicate 7843:function 7529:element' 7170:confluent 7116:whenever 6618:The term 6581:Reduction 6521:}, where 6084:, can be 5998:λ 5977:λ 5950:λ 5914:λ 5878:λ 5854:→ 5836:λ 5815:λ 5777:λ 5756:λ 5747:Ω 5707:λ 5663:→ 5645:λ 5613:λ 5569:→ 5551:λ 5458:λ 5417:→ 5399:λ 5326:λ 5286:λ 5250:λ 5217:λ 5147:λ 5112:λ 5083:λ 5054:λ 5018:λ 4985:λ 4897:λ 4834:λ 4789:λ 4754:λ 4718:λ 4685:λ 4531:≠ 4478:λ 4445:λ 4411:λ 4378:λ 4138:≠ 3694:λ 3665:λ 3506:λ 3472:are just 3372:λ 3343:λ 3281:λ 3272:λ 3263:λ 3216:↦ 3181:λ 3158:↦ 3122:λ 3078:λ 3047:which is 3000:λ 2988:λ 2873:λ 2835:λ 2783:λ 2770:example 1 2670:λ 2658:λ 2624:λ 2586:λ 2571:λ 2520:λ 2434:λ 2390:on input 2297:λ 2118:λ 2077:λ 2032:λ 1926:λ 1900:variable 1862:or as an 1646:↦ 1558:↦ 1549:↦ 1396:↦ 1345:_ 1267:↦ 1258:↦ 1206:↦ 1154:_ 1106:↦ 1062:⁡ 954:↦ 868:⁡ 855:_ 822:semantics 758:∧ 735:∧ 712:^ 679:^ 446:→ 422:λ 366:λ 360:→ 336:λ 128:λ 86:reduction 27:-calculus 16633:See also 16518:Concepts 16392:Telicity 16227:Coercion 16181:Negation 16176:Modality 16126:Anaphora 15949:Logicism 15942:timeline 15918:Concrete 15777:Validity 15747:T-schema 15740:Kripke's 15735:Tarski's 15730:semantic 15720:Strength 15669:submodel 15664:spectrum 15632:function 15480:Tarski's 15469:Elements 15456:geometry 15412:Robinson 15333:variable 15318:function 15291:spectrum 15281:Sentence 15237:variable 15180:Language 15133:Relation 15094:Automata 15084:Alphabet 15068:language 14922:-jection 14900:codomain 14886:Function 14847:Universe 14817:Infinite 14721:Relation 14504:Validity 14494:Argument 14392:theorem, 14075:Students 13938:Archived 13926:Archived 13743:(1965). 13667:11485010 13427:(2002). 13395:53087112 13053:(1984). 12951:15889861 12689:(2003). 11938:parallel 11826:and the 11781:meaning. 11776:11321602 11706:ACM site 11649:(1944). 11594:Archived 11517:esoteric 11513:Unlambda 11306:See also 11219:System F 10815:are the 10740:that is 10493:(CCCs). 10477:via the 10450:such as 10035:defined 9704:.(1, if 9661:.(1, if 9618:.(1, if 9575:.(1, if 9562:4 × (G ( 9548:−1)))) 4 9532:.(1, if 9519:−1)))) ( 9503:.(1, if 9194:.(1, if 9141:=: FIX G 9090:.(1, if 8995:.(1, if 8778:to mean 8733:.FIRST ( 8501:> 0. 8483:) 1)) (λ 8446:) 1)) (λ 7960:denotes 7760:n  7708:PLUS 2 3 7333:Notation 6288:Notation 6278:variable 6230:variable 6211:variable 4065:becomes 3762:Suppose 2804:, where 1871:currying 1310:currying 538:function 113:variable 16136:Binding 15891:Related 15688:Diagram 15586: ( 15565:Hilbert 15550:Systems 15545:Theorem 15423:of the 15368:systems 15148:Formula 15143:Grammar 15059: ( 15003:General 14716:Forcing 14701:Element 14621:Monadic 14396:paradox 14337:Theorem 14273:General 13885:, 2001 13771:6505810 13155:Bibcode 12943:2266170 12905:2371045 12864:2268117 12822:1968646 12780:1968337 12589:2317046 12581:2268280 12540:at the 12145:maps to 12099:axiom β 11579:(1977) 11446:hackers 11391:giving 11358:Clojure 11333:objects 11112:Futures 10953:Haskell 10793: = 10456:Haskell 10013:BU(CBU) 9571:4 × ((λ 9233:(FIX G) 8926:. Here 8906:by name 8769:library 8627:.FALSE) 8476:(PLUS ( 8439:(PLUS ( 8065:yields 7983:, then 6833:In the 6556:) ∪ FV( 6552:) = FV( 6536:) = FV( 6366:means λ 5804:. Here 5733:Haskell 3567:removed 2773:defines 2736:  2358:  1988:  1318:of the 1178:another 602:History 545:untyped 534:binding 278:. Both 51:binding 29:) is a 16565:Monads 16112:Topics 15654:finite 15417:Skolem 15370:  15345:Theory 15313:Symbol 15303:String 15286:atomic 15163:ground 15158:closed 15153:atomic 15109:ground 15072:syntax 14968:binary 14895:domain 14812:Finite 14577:finite 14435:Logics 14394:  14342:Theory 14212:Family 13967:using 13769:  13665:  13655:  13578:  13560:  13481:  13441:  13393:  13342:  13209:  13063:  12987:29 Dec 12978:  12949:  12941:  12903:  12862:  12820:  12778:  12699:  12669:  12642:  12587:  12579:  12493:FOLDOC 12472:letrec 12058:  12040:  12022:  12013:  11846:  11814:  11791:  11774:  11729:  11638:  11583:  11542:  11443:Scheme 11389:posets 11368:proofs 11235:These 11180:domain 11073:Eiffel 11037:Pascal 11022:lambda 10997:lambda 10987:Python 10797:  10730:decide 10373:, the 9206:−1)))) 9163:where 8878:letrec 8876:. The 8858:, for 8543:SECOND 8317:, but 8307:ISZERO 8016:> 0 7993:) = (λ 7816:(PLUS 7550:(PAIR 7216:, and 6957:), if 6652:reduct 6567:closed 6440:binder 6147:) ∈ Λ. 6126:) ∈ Λ. 6070:, ...; 4775:, and 4610:" for 2937:  2768:Here, 1006:mapped 727:” to “ 659:lambda 653:symbol 582:, and 553:weaker 437:  216:  16257:De se 16161:Focus 16119:Areas 16088:Scope 15644:Model 15392:Peano 15249:Proof 15089:Arity 15018:Naive 14905:image 14837:Fuzzy 14797:Empty 14746:union 14691:Class 14332:Model 14322:Lemma 14280:Axiom 13789:(PDF) 13767:S2CID 13721:arXiv 13663:S2CID 13635:arXiv 13600:(PDF) 13510:(PDF) 13463:(PDF) 13391:S2CID 13371:(PDF) 13316:(PDF) 13290:(PDF) 13251:(PDF) 13244:(PDF) 13145:arXiv 13141:(PDF) 13034:32:50 12947:S2CID 12939:JSTOR 12901:JSTOR 12860:JSTOR 12818:JSTOR 12776:JSTOR 12585:S2CID 12577:JSTOR 12526:(PDF) 12259:ASCII 11945:Notes 11772:S2CID 11658:(PDF) 11515:– An 11229:types 11187:model 11163:is a 11081:C++11 11069:Scala 10856:. If 10722:FALSE 10516:form. 10271:, or 10118:from 10037:above 10033:FALSE 10004:above 9490:G) 4 9481:G) 4 9418:)) (λ 9380:)) (λ 9342:)) (λ 9273:)) (λ 9178:(FIX 9106:−1))) 9014:−1))) 8872:with 8606:.TRUE 8597:FALSE 8539:FIRST 8515:FALSE 8505:Pairs 8450:.0) 0 8408:FALSE 8379:, if 8319:FALSE 8296:FALSE 8283:FALSE 8103:FALSE 8080:> 8075:when 8047:PRED 8028:pairs 7935:)) (λ 7875:PRED 7758:SUCC 7554:) NIL 7019:above 7013:up to 6969:∉ FV( 6949:) = λ 6931:) = λ 6885:, if 6826:(see 6824:scope 6820:masks 6783:with 6706:alpha 6620:redex 6540:) \ { 6517:) = { 6464:x x y 6424:bound 6141:then 6116:then 4608:fresh 3957:in a 2322:binds 994:tuple 565:below 549:typed 234:: An 15767:Type 15570:list 15374:list 15351:list 15340:Term 15274:rank 15168:open 15062:list 14874:Maps 14779:sets 14638:Free 14608:list 14358:list 14285:list 13841:2022 13653:ISBN 13576:ISBN 13535:2022 13492:2022 13479:ISBN 13439:ISBN 13402:2022 13353:2022 13340:ISBN 13298:2022 13207:ISBN 13061:ISBN 13016:2020 12989:2016 12976:ISBN 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5092:y 5089:. 5086:x 5063:x 5060:. 5057:x 5051:= 5048:) 5045:] 5042:x 5036:y 5033:[ 5030:y 5027:( 5024:. 5021:x 5015:= 5012:] 5009:x 5003:y 5000:[ 4997:) 4994:y 4991:. 4988:x 4982:( 4959:r 4935:y 4912:y 4909:) 4906:y 4903:. 4900:x 4894:( 4891:= 4888:) 4885:] 4882:y 4876:x 4873:[ 4870:x 4867:( 4864:) 4861:] 4858:y 4852:x 4849:[ 4846:) 4843:y 4840:. 4837:x 4831:( 4828:( 4825:= 4822:] 4819:y 4813:x 4810:[ 4807:) 4804:x 4801:) 4798:y 4795:. 4792:x 4786:( 4783:( 4763:x 4760:. 4757:x 4751:= 4748:) 4745:] 4742:y 4736:y 4733:[ 4730:x 4727:( 4724:. 4721:x 4715:= 4712:] 4709:y 4703:y 4700:[ 4697:) 4694:x 4691:. 4688:x 4682:( 4670:. 4658:r 4638:y 4618:r 4594:y 4586:( 4574:r 4554:y 4534:y 4528:x 4508:) 4505:] 4502:r 4496:x 4493:[ 4490:t 4487:( 4484:. 4481:y 4475:= 4472:] 4469:r 4463:x 4460:[ 4457:) 4454:t 4451:. 4448:y 4442:( 4420:t 4417:. 4414:x 4408:= 4405:] 4402:r 4396:x 4393:[ 4390:) 4387:t 4384:. 4381:x 4375:( 4353:) 4350:] 4347:r 4341:x 4338:[ 4335:s 4332:( 4329:) 4326:] 4323:r 4317:x 4314:[ 4311:t 4308:( 4305:= 4302:] 4299:r 4293:x 4290:[ 4287:) 4284:s 4265:t 4262:( 4241:y 4221:x 4201:y 4181:x 4161:r 4141:y 4135:x 4115:y 4112:= 4109:] 4106:r 4100:x 4097:[ 4094:y 4073:r 4053:x 4033:x 4013:r 3993:r 3990:= 3987:] 3984:r 3978:x 3975:[ 3972:x 3945:t 3925:x 3905:r 3885:] 3882:r 3876:x 3873:[ 3870:t 3850:y 3830:x 3810:r 3790:s 3770:t 3742:y 3722:x 3703:y 3700:. 3697:x 3674:x 3671:. 3668:x 3653:. 3641:s 3621:t 3601:s 3582:t 3555:x 3535:t 3515:t 3512:. 3509:x 3480:x 3460:x 3421:y 3401:x 3381:y 3378:. 3375:y 3352:x 3349:. 3346:x 3308:) 3305:) 3302:x 3299:g 3296:( 3293:f 3290:( 3287:. 3284:x 3278:. 3275:g 3269:. 3266:f 3239:y 3219:y 3213:x 3190:y 3187:. 3184:x 3161:x 3155:x 3131:x 3128:. 3125:x 3087:x 3084:. 3081:x 3055:x 3035:N 3015:) 3012:) 3009:x 3006:. 3003:x 2997:( 2994:. 2991:x 2985:( 2965:M 2945:N 2925:M 2905:x 2885:) 2882:x 2879:. 2876:x 2870:( 2850:x 2847:) 2844:x 2841:. 2838:x 2832:( 2812:B 2792:B 2789:. 2786:x 2763:x 2744:N 2724:M 2704:x 2685:) 2682:) 2679:x 2676:. 2673:x 2667:( 2664:. 2661:x 2655:( 2633:B 2630:. 2627:x 2604:) 2601:x 2598:) 2595:x 2592:. 2589:x 2583:( 2580:( 2577:. 2574:x 2555:y 2541:) 2538:y 2535:+ 2532:x 2529:( 2526:. 2523:x 2510:y 2496:y 2493:+ 2490:x 2487:= 2484:) 2481:x 2478:( 2475:f 2455:) 2452:y 2449:+ 2446:x 2443:( 2440:. 2437:x 2411:) 2408:s 2405:( 2402:t 2392:s 2388:t 2384:s 2380:t 2366:s 2346:t 2330:t 2326:x 2309:) 2306:t 2303:. 2300:x 2294:( 2274:f 2264:t 2250:2 2247:+ 2242:2 2238:x 2217:, 2214:2 2211:+ 2206:2 2202:x 2198:= 2195:) 2192:x 2189:( 2186:f 2166:f 2146:) 2143:2 2140:+ 2135:2 2131:x 2127:( 2124:. 2121:x 2108:t 2104:x 2086:t 2083:. 2080:x 2051:. 2046:2 2042:x 2038:. 2035:x 1999:) 1996:s 1976:t 1973:( 1963:s 1959:t 1938:) 1935:t 1932:. 1929:x 1923:( 1913:x 1909:t 1902:x 1883:C 1828:= 1806:2 1786:y 1764:2 1760:2 1756:+ 1751:2 1747:5 1743:= 1721:5 1701:x 1681:) 1678:2 1675:( 1672:) 1667:2 1663:y 1659:+ 1654:2 1650:5 1643:y 1640:( 1637:= 1616:) 1613:2 1610:( 1605:) 1600:) 1597:5 1594:( 1589:) 1584:) 1579:2 1575:y 1571:+ 1566:2 1562:x 1555:y 1552:( 1546:x 1541:( 1534:( 1517:, 1502:= 1479:2 1475:2 1471:+ 1466:2 1462:5 1458:= 1437:) 1434:2 1431:, 1428:5 1425:( 1422:) 1417:2 1413:y 1409:+ 1404:2 1400:x 1393:) 1390:y 1387:, 1384:x 1381:( 1378:( 1354:m 1351:u 1348:s 1342:e 1339:r 1336:a 1333:u 1330:q 1327:s 1293:) 1288:2 1284:y 1280:+ 1275:2 1271:x 1264:y 1261:( 1255:x 1227:2 1223:y 1219:+ 1214:2 1210:x 1203:) 1200:y 1197:, 1194:x 1191:( 1163:m 1160:u 1157:s 1151:e 1148:r 1145:a 1142:u 1139:q 1136:s 1109:x 1103:x 1077:x 1074:= 1071:) 1068:x 1065:( 1034:2 1030:y 1026:+ 1021:2 1017:x 1002:y 998:x 975:2 971:y 967:+ 962:2 958:x 951:) 948:y 945:, 942:x 939:( 907:2 903:y 899:+ 894:2 890:x 886:= 883:) 880:y 877:, 874:x 871:( 864:m 861:u 858:s 852:e 849:r 846:a 843:u 840:q 837:s 738:x 709:x 676:x 651:λ 470:) 467:] 464:N 458:x 455:[ 452:M 449:( 443:) 440:N 434:) 431:M 428:. 425:x 419:( 416:( 406:. 387:) 384:] 381:y 378:[ 375:M 372:. 369:y 363:( 357:) 354:] 351:x 348:[ 345:M 342:. 339:x 333:( 306:N 286:M 266:N 246:M 222:) 219:N 213:M 210:( 200:. 188:M 178:. 164:x 140:) 137:M 134:. 131:x 125:( 99:x 25:λ

Index

formal system
mathematical logic
computation
abstraction
application
binding
substitution
model of computation
Turing machine
Alonzo Church
foundations of mathematics
logically consistent
lambda terms
reduction
variable
lambda abstraction
application
: α-conversion
name collisions
: β-reduction
De Bruijn indexing
repeated application
Church–Rosser theorem
β-normal form
Iota and Jot
Turing complete
model of computation
Turing machine
binding
function

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