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Type theory

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14440: 251: 12662: 12672: 12682: 9767:, which means that any order of applying the rules will always end in the same result. However, some are not. In a normalizing type theory, the one-directional computation rules are called "reduction rules", and applying the rules "reduces" the term. If a rule is not one-directional, it is called a "conversion rule". 3982:
B" resembles a function from type "A" to type "B". For a variety of logics, the rules are similar to expressions in a programming language's types. The similarity goes farther, as applications of the rules resemble programs in the programming languages. Thus, the correspondence is often summarized as
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be viewed as type theories of a certain kind; this fact alone indicates that type theory is much more closely related to category theory than it is to set theory." In brief, a category can be viewed as a type theory by regarding its objects as types (or sorts), i.e. "Roughly speaking, a category may
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nature of type theory, where proving that a value exists requires a method to compute the value. The Axiom of Choice is less powerful in type theory than most set theories, because type theory's functions must be computable and, being syntax-driven, the number of terms in a type must be countable.
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Type theory has a built-in notion of computation. Thus, "1+1" and "2" are different terms in type theory, but they compute to the same value. Moreover, functions are defined computationally as lambda terms. In set theory, "1+1=2" means that "1+1" is just another way to refer the value "2". Type
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It is possible to include the law of excluded middle and double negation into a type theory, by rule or assumption. However, terms may not compute down to canonical terms and it will interfere with the ability to determine if two terms are judgementally equal to each other.
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Most of the type theories proposed as foundations are constructive, and this includes most of the ones used by proof assistants. It is possible to add non-constructive features to a type theory, by rule or assumption. These include operators on continuations such as
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published in 1910, 1912, and 1913. This system avoided contradictions suggested in Russell's paradox by creating a hierarchy of types and then assigning each concrete mathematical entity to a specific type. Entities of a given type were built exclusively of
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Provides a historical survey of the developments of the theory of types with a focus on the decline of the theory as a foundation of mathematics over the four decades following the publication of the second edition of 'Principia
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Sometimes, a type theory will add a few axioms. An axiom is a judgment that is accepted without a derivation using the rules of inference. They are often added to ensure properties that cannot be added cleanly through the rules.
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In set theory, an element is not restricted to one set. The element can appear in subsets and unions with other sets. In type theory, terms (generally) belong to only one type. Where a subset would be used, type theory can use a
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Inductive types are a general template for creating a large variety of types. In fact, all the types described above and more can be defined using the rules of inductive types. Two methods of generating inductive types are
2420: 5827: 5906: 10017:. This is because a type theory is defined by its rules of inference. This is a source of confusion for people familiar with Set Theory, where a theory is defined by both the rules of inference for a logic (such as 4845: 5682: 1853: 1261: 9198: 9020: 2747: 9885: 7979: 9144: 8037: 7060: 9071: 9770:
Some combinations of types are equivalent to other combinations of types. When functions are considered "exponentiation", the combinations of types can be written similarly to algebraic identities. Thus,
8317: 8221: 5741: 134:) is that, without proper axioms, it is possible to define the set of all sets that are not members of themselves; this set both contains itself and does not contain itself. Between 1902 and 1908, 8901: 780: 8828: 2654:, where the top-most rules need no assumptions. One example of a rule that does not require any inputs is one that states the type of a constant term. For example, to assert that there is a term 5319: 4749: 3740: 347:. Most of these systems use a type theory as the mathematical foundation for encoding proofs, which is not surprising, given the close connection between type theory and programming languages: 1195: 4348: 2808: 967: 10003: 9944: 8046: 9841: 6087: 6020: 4012:
Many programs that work with type theory (e.g., interactive theorem provers) also do type inferencing. It lets them select the rules that the user intends, with fewer actions by the user.
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To generate a particular judgment in type theory, there must be a rule to generate it, as well as rules to generate all of that rule's required inputs, and so on. The applied rules form a
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Some type theories allow for types of complex terms, such as functions or lists, to depend on the types of its arguments. For example, a type theory could have the dependent type
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Language Engineering and Rigorous Software Development: International LerNet ALFA Summer School 2008, Piriapolis, Uruguay, February 24 - March 1, 2008, Revised Tutorial Lectures
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of that type, thus preventing an entity from being defined using itself. This resolution of Russell's paradox is similar to approaches taken in other formal systems, such as
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using a horizontal line, with the required input judgments above the line and the resulting judgment below the line. For example, the following inference rule states a
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is a function from sets of entities to truth-values, i.e. a (indicator function of a) set of sets. This latter type is standardly taken to be the type of
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The most basic types are called atoms, and a term whose type is an atom is known as an atomic term. Common atomic terms included in type theories are
3016: 5747: 4057:(categories with products and exponentials and one non-terminal object) correspond to the untyped λ-calculus (observed independently by Lambek and 10541:
Montague, R. (1973) "The proper treatment of quantification in ordinary English". In K. J. J. Hintikka, J. M. E. Moravcsik, and P. Suppes (eds.),
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Although the initial motivation for category theory was far removed from foundationalism, the two fields turned out to have deep connections. As
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does not need to be added to type theory, because in most type theories it can be derived from the rules of inference. This is because of the
9302:{\displaystyle (\Pi \,\sigma \,\tau .{\mathsf {bool}}\to \sigma \to \tau \to (\Sigma \,x:{\textsf {bool}}.\mathrm {TF} \,x\,\sigma \,\tau ))} 4782: 142: 8431:, respectively. Dependent product and sum types commonly appear in function types and are frequently incorporated in programming languages. 5629: 1801: 1200: 13577: 12718: 10855: 4847:, which would be a function which takes in a function of natural numbers and returns a natural number. The convention is that the arrow is 7325:
There are foundational issues that can arise from dependent types if a theory is not careful about what dependencies are allowed, such as
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notion of equality. The judgments enforce that every term has a type. The type will restrict which rules can be applied to a term.
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Axioms can cause problems if they introduce terms without a way to compute on those terms. That is, axioms can interfere with the
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Strictly speaking, a simple type only allows for one input and one output, so a more faithful reading of the above type is that
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A good introduction to simple type theory for computer scientists; the system described is not exactly Church's STT though.
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Heineman, George T.; Bessai, Jan; Düdder, Boris; Rehof, Jakob (2016). "A long and winding road towards modular synthesis".
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In the modern literature, "type theory" refers to a typed system based around lambda calculus. One influential system is
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mathematics to serve as a new foundation for mathematics. There is ongoing research into mathematical foundations using
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Some theories also permit types to be dependent on terms instead of types. For example, a theory could have the type
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attempts to combine type theory and category theory. It focuses on equalities, especially equalities between types.
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may actually consist of complex terms and types that contain many function applications, not just single symbols.
14905: 13447: 13140: 12073: 10545:(Synthese Library, 49), Dordrecht: Reidel, 221–242; reprinted in Portner and Partee (eds.) 2002, pp. 17–35. See: 9628: 8376: 3959: 2214: 418: 310: 169: 85: 12881: 10042:"Univalence Axiom" holds that equivalence of types is equality of types. The research into this property led to 622:
nothing except the basic types, and what can be constructed from them by means of the previous clause are types.
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exists. Constructive mathematics does not allow the last step of removing the double negation to conclude that
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Bove, Ana; Dybjer, Peter (2009), Bove, Ana; Barbosa, Luís Soares; Pardo, Alberto; Pinto, Jorge Sousa (eds.),
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may also act as a foundation of mathematics. There are a number of differences between these two approaches.
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In type theory, proofs are types whereas in set theory, proofs are part of the underlying first-order logic.
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does not exist and refuting it by contradiction. The conclusion from that step is "it is not the case that
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of a type system with Curry–Howard correspondence. To be sound, such a system must have uninhabited types.
211: 184: 10171: 5275:, which is seen by applying the function application inference rule twice. Thus, the lambda term has type 5212: 3639: 14564: 14201: 14196: 13806: 13545: 13474: 12803: 12704: 12675: 12410: 11908: 11628: 9581: 8713: 8656: 8474: 7900: 7435: 7073: 6272:. The second reduction makes explicit the relationship between lambda expressions and function types: if 4040:
be thought of as a type theory shorn of its syntax." A number of significant results follow in this way:
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Elements of Formal Semantics: An Introduction to the Mathematical Theory of Meaning in Natural Language
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Ferreirós, José; Domínguez, José Ferreirós (2007). "X. Logic and Type Theory in the Interwar Period".
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Proponents of type theory will also point out its connection to constructive mathematics through the
9600: 9447: 7924: 7283: 7108: 6895: 5248: 5182: 4161: 4127: 4079:, has been a subject of active research since then; see the monograph of Jacobs (1999) for instance. 4044: 3587: 2677: 1919: 1637: 1564: 1020: 814: 453: 383: 344: 219: 188: 93: 12876: 8528:, and returns the list with the element at the end. The type annotation of such a function would be 4891:, and are called lambda terms. These terms are also defined inductively: a lambda term has the form 4854: 4754: 4680: 4566: 4068: 3939: 3062:
Under this intuitionistic interpretation, there are common types that act as the logical operators:
2989:"term introduction" rules define the canonical terms and constructor functions, like "pair" and "S". 2405:
say what judgments can be made, based on the existence of other judgments. Rules are expressed as a
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because it lacks a name. The concept of anonymous functions appears in many programming languages.
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A History of the Theory of Types: Developments After the Second Edition of 'Principia Mathematica'
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is the observed similarity between logics and programming languages. The implication in logic, "A
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that afflicted the original untyped lambda calculus. Church demonstrated that it could serve as a
20: 15106: 14647: 14093: 14070: 14031: 13917: 13858: 13504: 13424: 13268: 13212: 12825: 12577: 12511: 12402: 12218: 11878: 11649: 11625:— moderated e-mail forum focusing on type theory in computer science, operating since 1987. 11588: 11564: 10375: 9710:. Where a union would be used, type theory uses the sum type, which contains new canonical terms. 827: 434: 11609: 10852: 9760:
Terms usually belong to a single type. However, there are set theories that define "subtyping".
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Leveraging Applications of Formal Methods, Verification and Validation: Foundational Techniques
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input. If the type theory allows for dependent types, then it is possible to define a function
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which are interpreted as elements of the set of functions from entities to truth-values, i.e.
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Aarts, C.; Backhouse, R.; Hoogendijk, P.; Voermans, E.; van der Woude, J. (December 1992).
10165: 9764: 9659: 9560: 9149: 8626:{\displaystyle \mathrm {append} :(\Pi \,a.{\mathsf {list}}\,a\to a\to {\mathsf {list}}\,a)} 7501: 7403: 7351: 6729: 6687: 6559: 6522: 6136: 5939: 5512: 5350: 5035: 4536: 4466: 4440: 4091: 4087: 3182: 3158: 3137: 3108: 3087: 3048: 3024: 3015:, or constructive, logic. Formally, type theory is often cited as an implementation of the 3012: 2877: 2837: 2623: 2596: 2414: 2295: 2268: 2163: 2136: 1437: 1410: 1380: 1350: 1074: 994: 982: 299: 235: 123: 11622: 10673: 8394: 8322: 8226: 3965: 3781: 2995:"computation" rules specify how computation is performed with the type-specific functions. 290:, used type theory to encode mathematics on a computer. Martin-Löf specifically developed 8: 15101: 15066: 15011: 14955: 14858: 14843: 14813: 14793: 14768: 14637: 14622: 14415: 14306: 14291: 14271: 14228: 14115: 14065: 13991: 13936: 13873: 13666: 13661: 13609: 13377: 13366: 13038: 12938: 12866: 12857: 12853: 12788: 12783: 12637: 12562: 12478: 12463: 12228: 12008: 11965: 11960: 11857: 11847: 11819: 11087: 10452: 9577: 9573: 9533: 9383: 9357: 9324: 7838: 7326: 7318:: functions with vector length restrictions or length matching requirements, such as the 5833: 5072:. The following lambda term represents a function which doubles an input natural number. 4563:
Some terms may be declared directly as having a simple type, such as the following term,
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Covers type theory in depth, including polymorphic and dependent type extensions. Gives
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Computation takes place by repeated application of rules. Many types of theories are
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An identity type requires two terms of the same type and is written with the symbol
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The first reduction describes how to evaluate a lambda term: if a lambda expression
2992:"term elimination" rules define the other functions like "first", "second", and "R". 234:. Type theory is an active area of research, one direction being the development of 203: 74: 15131: 15056: 14945: 14723: 14393: 14388: 14281: 14238: 14060: 14021: 14016: 14001: 13827: 13784: 13681: 13479: 13429: 13003: 12965: 12455: 12339: 12306: 12101: 12023: 11912: 11898: 11893: 11842: 11829: 11754: 11707: 11439: 11431: 11383: 11382:, Lecture Notes in Computer Science, Berlin, Heidelberg: Springer, pp. 57–99, 11318: 11250: 11246: 11153: 10951: 10900: 10712: 10513: 10432: 10312: 10146: 6966: 6486:{\displaystyle (\lambda x.\mathrm {add} \,x\,x)\,2\rightarrow \mathrm {add} \,2\,2} 5837: 5620: 5150:{\displaystyle (\lambda x.\mathrm {add} \,x\,x):{\mathsf {nat}}\to {\mathsf {nat}}} 2406: 986: 831: 795: 485: 477: 473: 154: 135: 115: 31: 10504: 10401: 10274: 10237: 9658:. When a type theory encodes the concepts of "and" and "or" as types, it leads to 14935: 14838: 14733: 14698: 14374: 14364: 14318: 14301: 14256: 14218: 14120: 14040: 13847: 13774: 13747: 13735: 13641: 13555: 13529: 13484: 13452: 13253: 13055: 12998: 12948: 12913: 12871: 12526: 12420: 12392: 12286: 12238: 12223: 12208: 12063: 12058: 11998: 11888: 11862: 11814: 11759: 11157: 11054: 10859: 10777: 10680: 10659: 10652: 10459: 10386: 10382: 10058: 10050: 9749: 9722: 9632: 9620: 9588: 7337:
as a framework for studying various restrictions and levels of dependent typing.
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is a function which takes in a natural number and returns a function of the form
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If there are no assumptions, there will be nothing to the left of the turnstile.
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Labyrinth of thought: a history of set theory and its role in modern mathematics
10242:. Studies in Logic and the Foundations of Mathematics. Vol. 141. Elsevier. 5916:
Type theories that allow for lambda terms also include inference rules known as
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The power of type theories is in specifying how terms may be combined by way of
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with his simple theory of types, and explained his method in 1956, pages 47-68.
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is a notable area of research that mainly deals with equality in type theory.
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The complexities of equality in type theory make it an active research topic;
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The sum type depends on two types, and it is commonly written with the symbol
845:
introduced a theory of logical types into the social sciences; his notions of
15161: 14808: 14783: 14617: 14333: 14011: 13518: 13303: 13293: 13263: 13248: 12918: 12521: 11809: 10963: 10700: 10219:
An Introduction to Mathematical Logic and Type Theory: To Truth Through Proof
9444:
is a possible type. Canonical terms are created with a reflexivity function,
9320: 7345:
The product type depends on two types, and its terms are commonly written as
5822:{\displaystyle ((\mathrm {add} \,1)((\mathrm {add} \,2)\,0)):{\textsf {nat}}} 4155: 3947: 2410: 176: 127: 65: 57:. Two influential type theories that have been proposed as foundations are: 39: 11558: 11417: 11298:"Cubical Type Theory: A constructive interpretation of the univalence axiom" 11174: 10904: 8367:, dependent product and dependent sum types, allow for the theory to encode 6824:
The Boolean type has exactly 2 canonical terms. The type is usually written
1488:
Judgments may follow from assumptions. For example, one might say "assuming
15076: 14996: 14863: 14743: 14627: 14607: 14233: 14080: 13981: 13973: 13853: 13801: 13710: 13646: 13629: 13560: 13419: 13278: 12980: 12763: 12617: 12276: 11614: 11305:
21st International Conference on Types for Proofs and Programs (TYPES 2015)
10923:
Handbook of the Philosophy of Science. Volume 14: Philosophy of Linguistics
9730: 7894: 7842: 7346: 7311: 7005:
for zero. Canonical values larger than zero use iterated applications of a
6746:. The unit type is also used in proofs of type inhabitation. If for a type 3754:
Per Martin-Löf proposed his intuitionistic type theory as a foundation for
3636:
Because the law of excluded middle does not hold, there is no term of type
3036: 2999:
For examples of rules, an interested reader may follow Appendix A.2 of the
2531: 978: 422: 119: 14991: 14848: 14612: 14539: 14223: 13402: 13392: 13339: 13023: 12943: 12928: 12753: 12607: 12233: 12145: 11182: 11052: 10370: 10142: 7334: 7319: 7315: 5901:{\displaystyle \mathrm {add} \,1\,(\mathrm {add} \,2\,0):{\textsf {nat}}} 3307: 3246: 2922: 870: 846: 799: 540: 43: 27: 250: 15141: 14788: 14554: 14509: 14504: 13273: 13128: 13099: 12905: 12627: 12557: 12150: 11883: 11739: 11597:
book, which proposed homotopy type theory as a mathematical foundation.
11594: 11296:
Cohen, Cyril; Coquand, Thierry; Huber, Simon; Mörtberg, Anders (2016).
11233:
2021 36th Annual ACM/IEEE Symposium on Logic in Computer Science (LICS)
10985: 10955: 10724: 10316: 8388: 8348: 6553: 4840:{\displaystyle ({\mathsf {nat}}\to {\mathsf {nat}})\to {\mathsf {nat}}} 4260:, whose type may vary. For example, the following may be atomic terms. 4058: 3894:
does not exist". The last step is, by double negation, concluding that
3683:. Likewise, double negation does not hold, so there is no term of type 3371: 2425: 50: 11444: 10940:"Truth of a proposition, evidence of a judgement, validity of a proof" 5677:{\displaystyle (\mathrm {add} \,1):{\textsf {nat}}\to {\textsf {nat}}} 4435:
In addition to atomic terms, most modern type theories also allow for
3942:. However, these operators tend to break desirable properties such as 2762:
Generally, the desired conclusion of a proof in type theory is one of
1848:{\displaystyle \vdash \mathrm {S} :{\mathsf {nat}}\to {\mathsf {nat}}} 1256:{\displaystyle (\mathrm {if} \,\mathrm {true} \,0\,(\mathrm {S} \,0))} 309:
already had difficulty working with the widely accepted foundation of
14940: 14758: 14683: 14662: 14592: 14544: 14524: 14425: 14328: 13381: 13298: 13258: 13222: 13158: 12970: 12960: 12933: 12696: 12132: 12093: 10939: 10891:
Cooper, Robin (2005). "Records and Record Types in Semantic Theory".
10757: 10517: 6681: 5349:. Type theories which have functions also have the inference rule of 4510: 2527: 543:, respectively, and defines the set of types recursively as follows: 165: 10872: 10716: 10350:. Nato Science Series II. Vol. 62. Springer. pp. 213–259. 9714:
theory's computation does require a complicated concept of equality.
9599:, are based on the calculus for inductive constructions, which is a 2982:
Also, for each "by rule" type, there are 4 different kinds of rules
417:. Isabelle also supports foundations besides type theories, such as 14853: 14642: 14410: 14208: 13656: 13361: 12955: 12193: 11676: 11313: 11241: 10122: 10098: 9015:{\displaystyle \mathrm {TF} \colon {\mathsf {bool}}\to U\to U\to U} 442: 318: 287: 10049:"Law of Excluded Middle" is often added to satisfy users who want 4102:
was proposed, which is a homotopy type theory with normalization.
3758:. Constructive mathematics requires when proving "there exists an 3019:
of intuitionistic logic. Additionally, connections can be made to
2742:{\displaystyle {\begin{array}{c}\hline \vdash 0:nat\\\end{array}}} 14006: 12798: 10983: 10467:
A modern perspective on type theory: from its origins until today
9880:{\displaystyle {\mathbb {1} }+{\mathbb {1} }\cong {\mathbb {2} }} 111: 19:"Theory of types" redirects here. For an architectural term, see 10207: 7974:{\displaystyle \mathrm {left} :\sigma \to (\sigma \sqcup \tau )} 7538:. The product type is usually defined with eliminator functions 6499:
for types and terms, there are corresponding inference rules of
10465:
Kamareddine, Fairouz D.; Laan, Twan; Nederpelt, Rob P. (2004).
9139:{\displaystyle \mathrm {TF} \,\mathrm {false} \,\sigma \,\tau } 8032:{\displaystyle \mathrm {right} :\tau \to (\sigma \sqcup \tau )} 7055:{\displaystyle \mathrm {S} :{\mathsf {nat}}\to {\mathsf {nat}}} 4048: 3986:
The opposition of terms and types can also be viewed as one of
3035:
When used as a foundation, certain types are interpreted to be
425:
is an example of a proof system that only supports set theory.
391: 11053:
Henk Barendregt; Wil Dekkers; Richard Statman (20 June 2013).
9066:{\displaystyle \mathrm {TF} \,\mathrm {true} \,\sigma \,\tau } 3011:
The logical framework of a type theory bears a resemblance to
187:. Church's theory of types helped the formal system avoid the 14718: 13550: 12896: 12741: 10189: 10014: 9648: 9624: 8312:{\displaystyle \mathrm {match} \,f\,g\,(\mathrm {right} \,y)} 7837:
Besides ordered pairs, this type is used for the concepts of
5321:, which means it is a function taking a natural number as an 1862: 377: 355: 10862:." Handbook of the Philosophy of Science 14 (2012): 271-323. 9690:
is paired with a proof that the subset's property holds for
9670:
or use a dependently-typed product type, where each element
8216:{\displaystyle \mathrm {match} \,f\,g\,(\mathrm {left} \,x)} 7893:. In programming languages, sum types may be referred to as 2928:
A type theory usually has several rules, including ones to:
2766:. The decision problem of type inhabitation (abbreviated by 11192:. Handbook of the History of Logic. Vol. 6. Elsevier. 10761: 9662:, and does not necessarily have the law of excluded middle. 2972:
list all the interactions of equality, such as substitution
849:
and logical levels are based on Russell's theory of types.
335:
Much of the current research into type theory is driven by
10987:
Homotopy Type Theory: Univalent Foundations of Mathematics
5179:
and (implicit from the lambda term's type) must have type
460:) and its own type system was heavily influenced by them. 11295: 11147: 9319:
Following the notion of Curry-Howard Correspondence, the
6351:. Therefore, the lambda expression is equivalent to just 401:
UTT (Luo's Unified Theory of dependent Types) is used by
10464: 6965:
Natural numbers are usually implemented in the style of
5736:{\displaystyle ((\mathrm {add} \,2)\,0):{\textsf {nat}}} 3003:
book, or read Martin-Löf's Intuitionistic Type Theory.
2921:
shows that type inhabitation is strongly related to the
405:
which is both a programming language and proof assistant
175:
Type theory is particularly popular in conjunction with
14484: 10776:
Chatzikyriakidis, Stergios; Luo, Zhaohui (2017-02-07).
10703:(1940). "A formulation of the simple theory of types". 488:
extensively use type constructors to define the types (
183:. One notable early example of type theory is Church's 8779:, which takes three arguments and behaves as follows. 4098:
mostly by its handling of the equality type. In 2016,
2713: 445:, has a connection to type theory. A prime example is 46:. Type theory is the academic study of type systems. 11665:
Summer 2015 Types, Logic, Semantics, and Verification
10506:
The evolution of type theory in logic and mathematics
9952: 9893: 9849: 9813: 9777: 9696: 9676: 9536: 9501: 9481: 9450: 9412: 9386: 9360: 9340: 9201: 9176: 9152: 9101: 9079: 9031: 8966: 8933: 8909: 8896:{\displaystyle \mathrm {if} \,\mathrm {false} \,x\,y} 8858: 8836: 8788: 8760: 8716: 8696: 8659: 8639: 8534: 8514: 8477: 8440: 8417: 8397: 8325: 8255: 8229: 8162: 8049: 7987: 7932: 7903: 7879: 7859: 7819: 7766: 7744: 7694: 7616: 7544: 7524: 7504: 7484: 7464: 7438: 7406: 7386: 7354: 7286: 7266: 7223: 7196: 7170: 7137: 7117: 7076: 7014: 6975: 6929: 6898: 6876: 6854: 6830: 6798: 6772: 6752: 6732: 6710: 6690: 6654: 6628: 6608: 6582: 6562: 6525: 6505: 6422: 6400: 6377: 6357: 6337: 6317: 6278: 6258: 6238: 6218: 6198: 6163: 6139: 6119: 6095: 6050: 6028: 5965: 5942: 5922: 5846: 5750: 5691: 5632: 5595: 5565: 5535: 5515: 5485: 5465: 5445: 5425: 5405: 5379: 5359: 5281: 5251: 5215: 5185: 5165: 5080: 5058: 5038: 5018: 4998: 4972: 4952: 4932: 4897: 4857: 4785: 4757: 4711: 4683: 4599: 4569: 4539: 4519: 4489: 4469: 4449: 4394: 4357: 4306: 4269: 4229: 4195: 4164: 4130: 3968: 3920: 3900: 3880: 3860: 3833: 3813: 3784: 3764: 3689: 3642: 3590: 3545: 3490: 3445: 3408: 3381: 3344: 3317: 3280: 3256: 3219: 3192: 3161: 3140: 3111: 3090: 2900: 2880: 2860: 2840: 2820: 2772: 2710: 2680: 2660: 2626: 2599: 2579: 2559: 2539: 2423: 2371: 2345: 2325: 2298: 2271: 2217: 2193: 2166: 2139: 2091: 2067: 2047: 2027: 1994: 1970: 1950: 1922: 1889: 1868: 1804: 1695: 1673: 1640: 1597: 1567: 1547: 1514: 1494: 1467: 1440: 1413: 1383: 1353: 1330: 1307: 1281: 1203: 1159: 1127: 1107: 1082: 1057: 1023: 1003: 925: 901: 878: 775:{\displaystyle \langle \langle e,t\rangle ,t\rangle } 744: 708: 688: 668: 632: 593: 573: 553: 525: 505: 10046:, where the property holds without needing an axiom. 9721:. Type theory can encode numbers as functions using 8823:{\displaystyle \mathrm {if} \,\mathrm {true} \,x\,y} 7322:, can encode this requirement as part of the type. 4439:. Function types introduce an arrow symbol, and are 10775: 9635:, abbreviated ZFC. Type theories having sufficient 2969:
define substitution for application of lambda terms
499:The most common construction takes the basic types 11567:article at the Stanford Encyclopedia of Philosophy 11088:"Rules to Martin-Löf's Intuitionistic Type Theory" 10483: 10346:. In Schwichtenberg, H.; Steinbruggen, R. (eds.). 10068:Axiom of choice § In constructive mathematics 9997: 9938: 9879: 9835: 9799: 9702: 9682: 9548: 9522: 9487: 9467: 9436: 9398: 9372: 9346: 9301: 9187: 9158: 9138: 9085: 9065: 9014: 8952: 8915: 8895: 8842: 8822: 8771: 8739: 8702: 8682: 8645: 8625: 8520: 8500: 8463: 8423: 8403: 8335: 8311: 8239: 8215: 8145: 8031: 7973: 7915: 7885: 7865: 7825: 7805: 7750: 7730: 7677: 7602: 7530: 7510: 7490: 7470: 7450: 7424: 7392: 7372: 7302: 7272: 7252: 7202: 7182: 7156: 7123: 7099: 7054: 6997: 6949: 6915: 6884: 6862: 6840: 6816:, which is to say it must have one or more terms. 6804: 6784: 6758: 6738: 6718: 6696: 6684:has exactly 1 canonical term. The type is written 6660: 6640: 6614: 6590: 6568: 6531: 6511: 6485: 6406: 6383: 6363: 6343: 6331:is a function term because it is being applied to 6323: 6303: 6264: 6244: 6224: 6204: 6184: 6145: 6125: 6101: 6081: 6034: 6014: 5948: 5928: 5900: 5836:; however, by convention, function application is 5821: 5735: 5676: 5611: 5581: 5551: 5521: 5501: 5471: 5451: 5431: 5411: 5391: 5365: 5314:{\displaystyle {\mathsf {nat}}\to {\mathsf {nat}}} 5313: 5267: 5237: 5201: 5171: 5149: 5064: 5044: 5024: 5004: 4984: 4958: 4938: 4918: 4871: 4839: 4771: 4744:{\displaystyle {\mathsf {nat}}\to {\mathsf {nat}}} 4743: 4697: 4667: 4583: 4545: 4525: 4501: 4475: 4455: 4419: 4379: 4342: 4291: 4248: 4215: 4181: 4146: 3974: 3926: 3906: 3886: 3866: 3839: 3819: 3799: 3770: 3735:{\displaystyle \Pi A.((A\to \bot )\to \bot )\to A} 3734: 3675: 3620: 3575: 3520: 3475: 3420: 3393: 3356: 3329: 3292: 3265: 3231: 3204: 3167: 3146: 3117: 3096: 2906: 2886: 2866: 2846: 2826: 2802: 2741: 2696: 2666: 2639: 2612: 2585: 2565: 2545: 2518: 2377: 2351: 2331: 2311: 2284: 2255: 2199: 2179: 2152: 2123: 2073: 2053: 2033: 2012: 1976: 1956: 1934: 1895: 1874: 1847: 1786: 1679: 1656: 1626: 1583: 1553: 1533: 1500: 1473: 1453: 1426: 1396: 1366: 1336: 1313: 1287: 1255: 1189: 1145: 1113: 1093: 1065: 1040: 1009: 961: 907: 884: 774: 726: 694: 674: 650: 611: 579: 559: 531: 511: 456:was developed for manipulating type theories (see 11577:Calculus of Constructions / Typed Lambda Calculus 11344:: CS1 maint: DOI inactive as of September 2024 ( 11227:Sterling, Jonathan; Angiuli, Carlo (2021-06-29). 10779:Modern Perspectives in Type-Theoretical Semantics 2986:"type formation" rules say how to create the type 1190:{\displaystyle (\mathrm {S} \,(\mathrm {S} \,0))} 15159: 14951:Segmented discourse representation theory (SDRT) 8927:The return type of this function depends on its 6766:, it is consistent to derive a function of type 6622:, it is consistent to derive a function of type 6495:In type theories that also establish notions of 4343:{\displaystyle \mathrm {true} :{\mathsf {bool}}} 2803:{\displaystyle \exists t.\Gamma \vdash t:\tau ?} 1861:of the judgment. Capital greek letters, such as 1664:". Such judgments are formally written with the 962:{\displaystyle \mathrm {term} :{\mathsf {type}}} 11607: 11464:"Programming with Math (Exploring Type Theory)" 11226: 9530:returns the canonical term inhabiting the type 5529:. For example, if one knows the type notations 9998:{\displaystyle A^{B\times C}\cong (A^{B})^{C}} 9939:{\displaystyle A^{B+C}\cong A^{B}\times A^{C}} 9755: 9606: 8358: 3953: 437:, such as the type checking algorithms in the 14470: 12712: 11716:Note: This template roughly follows the 2012 11692: 11059:. Cambridge University Press. pp. 1–66. 10592: 10279:The Computer Science and Engineering Handbook 10132:UTT (Luo's Unified Theory of dependent Types) 9836:{\displaystyle {\mathbb {1} }\times A\cong A} 6082:{\displaystyle (\lambda v.t\,v)\rightarrow t} 6015:{\displaystyle (\lambda v.t)\,s\rightarrow t} 3006: 11190:Sets and Extensions in the Twentieth Century 10873:Generalized quantifiers and natural language 10174:is an implementation of homotopy type theory 4887:New function terms may be constructed using 869:. Most logics have judgments asserting "The 769: 760: 748: 745: 721: 709: 645: 633: 606: 594: 138:proposed various solutions to this problem. 49:Some type theories serve as alternatives to 10512:(PhD). Eindhoven University of Technology. 10106:is often used to define other type theories 5619:, then the following type notations can be 3749: 2256:{\displaystyle \Gamma \vdash t_{1}=t_{2}:T} 1857:The list of assumptions on the left is the 738:of sets of entities. An expression of type 286:The first computer proof assistant, called 281: 14477: 14463: 12904: 12719: 12705: 11699: 11685: 11650:Oregon Programming Languages Summer School 11418:"Introduction to generalized type systems" 11373: 10984:The Univalent Foundations Program (2013). 10937: 10632: 10575: 10216: 9580:. A method that only uses lambda terms is 8391:, they are often written with the symbols 7314:. This allows for greater specificity and 6598:. One use for the empty type is proofs of 6556:has no terms. The type is usually written 3850:An example of a non-constructive proof is 2939:add an assumption to the context (context 11443: 11415: 11322: 11312: 11240: 10674:(rev. Mon Oct 12, 2020) Russell’s Paradox 10645: 10587:documentation, optimization, and dispatch 10369:Intended as a type theory counterpart of 10335: 9872: 9862: 9852: 9816: 9780: 9729:, and the construction closely resembles 9516: 9289: 9285: 9281: 9265: 9256: 9212: 9208: 9132: 9128: 9110: 9059: 9055: 9040: 8889: 8885: 8867: 8816: 8812: 8797: 8733: 8676: 8616: 8587: 8564: 8494: 8347:The sum type is used for the concepts of 8329: 8302: 8281: 8277: 8273: 8233: 8206: 8188: 8184: 8180: 8076: 7787: 7712: 7650: 7646: 7575: 7571: 7246: 7111:of terms, where each term must have type 7093: 6878: 6856: 6833: 6726:and the single canonical term is written 6712: 6584: 6542: 6479: 6475: 6457: 6450: 6446: 6371:, as both take in one argument and apply 6294: 6066: 5984: 5893: 5881: 5877: 5862: 5858: 5814: 5799: 5792: 5768: 5728: 5716: 5709: 5669: 5659: 5647: 5604: 5574: 5544: 5492: 5328:A lambda term is often referred to as an 5231: 5227: 5108: 5104: 4851:, so the parentheses may be dropped from 3017:Brouwer–Heyting–Kolmogorov interpretation 2124:{\displaystyle \Gamma \vdash T_{1}=T_{2}} 1761: 1757: 1753: 1617: 1613: 1609: 1243: 1234: 1230: 1215: 1177: 1168: 1136: 852: 210:, which was proposed as a foundation for 11552: 11352: 10747:Introduction To Mathematical Logic Vol 1 10695: 10693: 10691: 10689: 10399: 10272: 10073: 9654:Classical set theory and logic have the 8373:universal and existential quantification 7806:{\displaystyle \mathrm {second} \,(s,t)} 4509:is the type of a function which takes a 3043:out of types. However, the logic is not 1627:{\displaystyle (\mathrm {if} \,x\,y\,y)} 861:, which is to say it is a collection of 428: 11589:Programming in Martin-Löf's Type Theory 11229:"Normalization for Cubical Type Theory" 10431: 10381: 10306: 9800:{\displaystyle {\mathbb {0} }+A\cong A} 7731:{\displaystyle \mathrm {first} \,(s,t)} 6394:For example, the following term may be 6311:is a lambda term, then it must be that 5340: 4082: 3051:, which is to say it does not have the 3030: 2365:Some textbooks use a triple equal sign 15160: 12726: 12416:Knowledge representation and reasoning 10890: 10813: 10699: 10640:Getting Started With Julia Programming 10549:, Stanford Encyclopedia of Philosophy. 10403:Type Theory and Functional Programming 10235: 10035:Some commonly encountered axioms are: 9230: 9227: 9224: 9221: 8989: 8986: 8983: 8980: 8945: 8942: 8939: 8936: 8728: 8725: 8722: 8719: 8671: 8668: 8665: 8662: 8611: 8608: 8605: 8602: 8582: 8579: 8576: 8573: 8489: 8486: 8483: 8480: 7295: 7292: 7289: 7241: 7238: 7235: 7232: 7229: 7226: 7149: 7146: 7143: 7140: 7088: 7085: 7082: 7079: 7047: 7044: 7041: 7031: 7028: 7025: 6990: 6987: 6984: 5306: 5303: 5300: 5290: 5287: 5284: 5260: 5257: 5254: 5194: 5191: 5188: 5142: 5139: 5136: 5126: 5123: 5120: 4832: 4829: 4826: 4813: 4810: 4807: 4797: 4794: 4791: 4736: 4733: 4730: 4720: 4717: 4714: 4657: 4654: 4651: 4641: 4638: 4635: 4622: 4619: 4616: 4412: 4409: 4406: 4403: 4372: 4369: 4366: 4335: 4332: 4329: 4326: 4284: 4281: 4278: 4241: 4238: 4235: 4232: 4139: 4136: 4133: 2951:use an assumption to create a variable 2689: 2686: 2683: 1840: 1837: 1834: 1824: 1821: 1818: 1779: 1776: 1773: 1735: 1732: 1729: 1713: 1710: 1707: 1704: 1649: 1646: 1643: 1576: 1573: 1570: 1526: 1523: 1520: 1517: 1481: 954: 951: 948: 945: 358:, often to define other type theories; 14906:Discourse representation theory (DRT) 14458: 12700: 12441:Philosophy of artificial intelligence 11680: 11579:textbook style paper by Helmut Brandl 11503:from the original on 22 December 2021 11457: 11455: 11369: 11367: 11291: 11289: 11082: 11080: 11078: 11076: 11048: 11046: 11044: 11042: 11040: 11038: 11036: 11034: 10979: 10977: 10975: 10973: 10933: 10931: 10686: 10664: 10563: 8633:, which can be read as "for any type 7253:{\displaystyle {\mathsf {vector}}\,n} 2854:, decide whether there exists a term 2396: 1271:Most type theories have 4 judgments: 376:computational type theory is used by 222:, which is used as the foundation by 11760:Energy consumption (Green computing) 11706: 11601: 11561:, which has articles on many topics. 11461: 11235:. Rome, Italy: IEEE. pp. 1–15. 11180: 10739: 10605: 10570: 10502: 10212:. Technische Universiteit Eindhoven. 5238:{\displaystyle \mathrm {add} \,x\,x} 4047:correspond to the typed λ-calculus ( 3676:{\displaystyle \Pi a.A+(A\to \bot )} 2975:define a hierarchy of type universes 2751: 2526:The rules are syntactic and work by 2210: 480:and its descendants. In particular, 409:Many type theories are supported by 361:many type theories which fall under 245: 114:in a mathematical equation based on 14819:Quantificational variability effect 14486:Formal semantics (natural language) 12446:Distributed artificial intelligence 11718:ACM Computing Classification System 11129:from the original on 13 August 2023 10871:Barwise, Jon; Cooper, Robin (1981) 10671:Stanford Encyclopedia of Philosophy 10392:Stanford Encyclopedia of Philosophy 9331:that type theory already provides. 8740:{\displaystyle {\mathsf {list}}\,a} 8683:{\displaystyle {\mathsf {list}}\,a} 8501:{\displaystyle {\mathsf {list}}\,a} 7916:{\displaystyle \sigma \sqcup \tau } 7451:{\displaystyle \sigma \times \tau } 7100:{\displaystyle {\mathsf {list}}\,a} 7065: 6672:, which is to say it has no terms. 6212:, one replaces every occurrence of 4966:is a term, and its type is notated 4065:locally cartesian closed categories 3807:", one must construct a particular 3576:{\displaystyle \exists a\in A,P(a)} 3476:{\displaystyle \forall a\in A,P(a)} 727:{\displaystyle \langle e,t\rangle } 651:{\displaystyle \langle a,b\rangle } 612:{\displaystyle \langle a,b\rangle } 468:Type theory is also widely used in 324: 110:Type theory was created to avoid a 94:Calculus of Inductive Constructions 21:Form (architecture) § Theories 13: 11951:Integrated development environment 11452: 11364: 11286: 11073: 11031: 10970: 10928: 10210:"A Relational Theory of Datatypes" 10200: 10159: 10053:, instead of intuitionistic logic. 9566: 9523:{\displaystyle \mathrm {refl} \,t} 9512: 9509: 9506: 9503: 9461: 9458: 9455: 9452: 9329:judgmental (syntactic) equivalence 9277: 9274: 9253: 9205: 9181: 9178: 9124: 9121: 9118: 9115: 9112: 9106: 9103: 9051: 9048: 9045: 9042: 9036: 9033: 8971: 8968: 8881: 8878: 8875: 8872: 8869: 8863: 8860: 8808: 8805: 8802: 8799: 8793: 8790: 8765: 8762: 8561: 8551: 8548: 8545: 8542: 8539: 8536: 8457: 8454: 8451: 8448: 8445: 8442: 8418: 8398: 8298: 8295: 8292: 8289: 8286: 8269: 8266: 8263: 8260: 8257: 8202: 8199: 8196: 8193: 8176: 8173: 8170: 8167: 8164: 8073: 8063: 8060: 8057: 8054: 8051: 8001: 7998: 7995: 7992: 7989: 7943: 7940: 7937: 7934: 7783: 7780: 7777: 7774: 7771: 7768: 7708: 7705: 7702: 7699: 7696: 7643: 7633: 7630: 7627: 7624: 7621: 7618: 7568: 7558: 7555: 7552: 7549: 7546: 7016: 6960: 6943: 6940: 6937: 6934: 6931: 6909: 6906: 6903: 6900: 6892:. The canonical terms are usually 6773: 6691: 6635: 6563: 6471: 6468: 6465: 6442: 6439: 6436: 5873: 5870: 5867: 5854: 5851: 5848: 5788: 5785: 5782: 5764: 5761: 5758: 5705: 5702: 5699: 5643: 5640: 5637: 5335: 5223: 5220: 5217: 5100: 5097: 5094: 4865: 4862: 4859: 4765: 4762: 4759: 4691: 4688: 4685: 4607: 4604: 4601: 4577: 4574: 4571: 4553:. Types of this form are known as 4420:{\displaystyle y:{\mathsf {bool}}} 4317: 4314: 4311: 4308: 4292:{\displaystyle 42:{\mathsf {nat}}} 4209: 4206: 4203: 4200: 4197: 4175: 4172: 4169: 4166: 4110: 4020: 3854:. The first step is assuming that 3720: 3711: 3690: 3667: 3643: 3591: 3546: 3491: 3446: 3287: 3257: 3162: 3141: 3112: 3091: 2901: 2821: 2782: 2773: 2712: 2560: 2540: 2490: 2484: 2451: 2428: 2346: 2218: 2194: 2092: 2068: 1995: 1971: 1923: 1890: 1869: 1809: 1605: 1602: 1321: 1295: 1239: 1226: 1223: 1220: 1217: 1211: 1208: 1173: 1164: 1132: 1087: 1084: 1059: 1034: 1031: 1028: 1025: 936: 933: 930: 927: 837: 82:computerized proof-writing systems 14: 15189: 12426:Automated planning and scheduling 11956:Software configuration management 11547: 11423:Journal of Functional Programming 11360:(2015) Getting Started with Julia 11000: 10919:Type theory and semantics in flux 10853:Type theory and semantics in flux 10683:3. Early Responses to the Paradox 10341:"Naïve Computational Type Theory" 10239:Categorical Logic and Type Theory 9744:, its connection to logic by the 8464:{\displaystyle \mathrm {append} } 8434:For example, consider a function 6998:{\displaystyle 0:{\mathsf {nat}}} 5612:{\displaystyle 2:{\textsf {nat}}} 5582:{\displaystyle 1:{\textsf {nat}}} 5552:{\displaystyle 0:{\textsf {nat}}} 4430: 4380:{\displaystyle x:{\mathsf {nat}}} 4015: 4001: 3827:and a proof that it has property 2978:assert the existence of new types 2339:and are equal (under assumptions 2013:{\displaystyle \Gamma \vdash t:T} 1146:{\displaystyle (\mathrm {S} \,0)} 14438: 12680: 12670: 12661: 12660: 11660:Robert Harper's talks on YouTube 11652:, many lectures and some notes. 11631:: "Introduction to Type Theory." 11334:from the original on 2022-10-09. 10893:Journal of Logic and Computation 10537:from the original on 2022-10-09. 10367:from the original on 2022-10-09. 9314: 8953:{\displaystyle {\mathsf {bool}}} 7157:{\displaystyle {\mathsf {list}}} 6950:{\displaystyle \mathrm {false} } 6841:{\displaystyle {\textsf {bool}}} 6304:{\displaystyle (\lambda v.t\,v)} 5392:{\displaystyle \sigma \to \tau } 5325:and returning a natural number. 4985:{\displaystyle \sigma \to \tau } 4502:{\displaystyle \sigma \to \tau } 4249:{\displaystyle {\mathsf {bool}}} 4216:{\displaystyle \mathrm {false} } 4035:writes: "In fact categories can 2704:, one would write the following. 1987: 1915: 1534:{\displaystyle {\mathsf {bool}}} 812:representation framework, using 386:and its derivatives are used by 249: 12671: 12074:Computational complexity theory 11533:from the original on 2022-01-19 11515: 11485: 11474:from the original on 2022-01-22 11409: 11275:from the original on 2023-08-13 11220: 11209:from the original on 2018-04-17 11141: 11111: 11100:from the original on 2021-10-21 11019:from the original on 2022-10-09 10994: 10911: 10884: 10865: 10845: 10834:from the original on 2023-08-10 10807: 10796:from the original on 2023-08-10 10769: 10420:from the original on 2021-03-23 10311:. Lambert Academic Publishing. 10295:from the original on 2008-04-10 10281:. CRC Press. pp. 2208–36. 10256:from the original on 2023-08-10 10013:Most type theories do not have 9468:{\displaystyle \mathrm {refl} } 9323:is a type introduced to mirror 7340: 7303:{\displaystyle {\mathsf {nat}}} 6916:{\displaystyle \mathrm {true} } 6819: 5268:{\displaystyle {\mathsf {nat}}} 5202:{\displaystyle {\mathsf {nat}}} 4882: 4751:. The parentheses clarify that 4182:{\displaystyle \mathrm {true} } 4147:{\displaystyle {\mathsf {nat}}} 4115: 3621:{\displaystyle \Sigma a:A.P(a)} 2697:{\displaystyle {\mathsf {nat}}} 2450: 1935:{\displaystyle \Gamma \vdash T} 1657:{\displaystyle {\mathsf {nat}}} 1584:{\displaystyle {\mathsf {nat}}} 1374: 1041:{\displaystyle \mathrm {true} } 241: 14901:Combinatory categorial grammar 11858:Network performance evaluation 11416:Barendegt, Henk (April 1991). 11251:10.1109/LICS52264.2021.9470719 11188:. In Kanamory, Akihiro (ed.). 10938:Martin-Löf, Per (1987-12-01). 10820:. Edinburgh University Press. 10751: 10543:Approaches to Natural Language 10439:. Cambridge University Press. 9986: 9972: 9296: 9293: 9250: 9247: 9241: 9235: 9202: 9006: 9000: 8994: 8620: 8597: 8591: 8558: 8306: 8282: 8210: 8189: 8140: 8134: 8131: 8119: 8116: 8113: 8107: 8101: 8098: 8095: 8089: 8083: 8070: 8026: 8014: 8011: 7968: 7956: 7953: 7800: 7788: 7725: 7713: 7672: 7666: 7640: 7597: 7591: 7565: 7419: 7407: 7367: 7355: 7174: 7036: 6776: 6632: 6461: 6454: 6423: 6298: 6279: 6179: 6164: 6073: 6070: 6051: 6009: 5994: 5988: 5981: 5966: 5885: 5863: 5806: 5803: 5796: 5778: 5775: 5772: 5754: 5751: 5720: 5713: 5695: 5692: 5664: 5651: 5633: 5496: 5486: 5383: 5295: 5131: 5112: 5081: 4976: 4913: 4898: 4872:{\displaystyle \mathrm {add} } 4821: 4818: 4802: 4786: 4772:{\displaystyle \mathrm {add} } 4725: 4698:{\displaystyle \mathrm {add} } 4662: 4646: 4630: 4627: 4584:{\displaystyle \mathrm {add} } 4493: 4124:, often notated with the type 4105: 3969: 3940:call with current continuation 3794: 3788: 3726: 3723: 3717: 3714: 3708: 3702: 3699: 3670: 3664: 3658: 3615: 3609: 3570: 3564: 3515: 3509: 3470: 3464: 3284: 3223: 3196: 2932:create a judgment (known as a 2874:that can be assigned the type 1829: 1765: 1743: 1621: 1598: 1250: 1247: 1235: 1204: 1184: 1181: 1169: 1160: 1140: 1128: 463: 141:By 1908, Russell arrived at a 1: 14679:Antecedent-contained deletion 14399:History of mathematical logic 12229:Multimedia information system 12214:Geographic information system 12204:Enterprise information system 11793:Computer systems organization 10705:The Journal of Symbolic Logic 10626: 10277:. In Tucker, Allen B. (ed.). 9188:{\displaystyle \mathrm {if} } 8772:{\displaystyle \mathrm {if} } 8043:, and an eliminator function 7214:of all types in the theory. 7107:, which should correspond to 6547: 6185:{\displaystyle (\lambda v.t)} 5911: 4919:{\displaystyle (\lambda v.t)} 4483:are types, then the notation 2417:rule for judgmental equality. 2084: 1964:is a type (under assumptions 1909:Formal notation for judgments 1094:{\displaystyle \mathrm {if} } 132:The Foundations of Arithmetic 16:Concept in mathematical logic 14324:Primitive recursive function 12588:Computational social science 12176:Theoretical computer science 11989:Software development process 11765:Electronic design automation 11750:Very Large Scale Integration 11637:of summer schools 2005–2008 11183:"Types, Sets and Categories" 11158:10.1007/978-3-319-47166-2_21 10348:Proof and System-Reliability 10085:Simply typed lambda calculus 8371:by acting as equivalents to 6969:. There is a canonical term 6885:{\displaystyle \mathbb {2} } 6863:{\displaystyle \mathbb {B} } 6719:{\displaystyle \mathbb {1} } 6675: 6591:{\displaystyle \mathbb {0} } 3521:{\displaystyle \Pi a:A.P(a)} 1266: 1066:{\displaystyle \mathrm {S} } 1048:, and functions such as the 784:natural language quantifiers 470:formal theories of semantics 195:and it was referred to as a 185:simply typed lambda calculus 149:, both of which appeared in 32:theoretical computer science 7: 12411:Natural language processing 12199:Information storage systems 11635:Types Project lecture notes 11610:"Computational type theory" 11608:Robert L. Constable (ed.). 11448:– via Cambridge Core. 11388:10.1007/978-3-642-03153-3_2 11324:10.4230/LIPIcs.CVIT.2016.23 10814:Winter, Yoad (2016-04-08). 10619:, as an anonymous function. 10307:Collins, Jordan E. (2012). 10178: 9756:Properties of type theories 9629:Zermelo–Fraenkel set theory 9611:The most commonly accepted 9607:Differences from set theory 8379:. As they also connect to 8377:Curry–Howard Correspondence 8359:Dependent products and sums 7848: 7310:encoding the length of the 5623:from function application. 4533:and returns a term of type 4045:cartesian closed categories 3960:Curry–Howard correspondence 3954:Curry-Howard correspondence 1101:. Thus some terms could be 824:natural language processing 311:Zermelo–Fraenkel set theory 170:Zermelo-Fraenkel set theory 10: 15194: 14560:Syntax–semantics interface 13388:Schröder–Bernstein theorem 13115:Monadic predicate calculus 12774:Foundations of mathematics 12327:Human–computer interaction 12297:Intrusion detection system 12209:Social information systems 12194:Database management system 11583:Intuitionistic Type Theory 11565:Intuitionistic Type Theory 11056:Lambda Calculus with Types 10876:Linguistics and Philosophy 10679:December 18, 2021, at the 10488:(2nd ed.). Springer. 10217:Andrews B., Peter (2002). 10168:explores equality of types 10094:intuitionistic type theory 9613:foundation for mathematics 6785:{\displaystyle \top \to a} 6641:{\displaystyle a\to \bot } 5439:, then the application of 4096:intuitionistic type theory 4005: 3293:{\displaystyle A\to \bot } 3007:Connections to foundations 2755: 702:. Thus one has types like 328: 305:Mathematicians working in 292:intuitionistic type theory 208:intuitionistic type theory 103: 99: 71:Intuitionistic type theory 18: 15094: 15052:Question under discussion 15002:Conversational scoreboard 14979: 14883: 14876: 14779:Intersective modification 14764:Homogeneity (linguistics) 14671: 14580: 14573: 14492: 14434: 14421:Philosophy of mathematics 14370:Automated theorem proving 14352: 14247: 14079: 13972: 13824: 13541: 13517: 13495:Von Neumann–Bernays–Gödel 13440: 13334: 13238: 13136: 13127: 13054: 12989: 12895: 12817: 12734: 12656: 12593:Computational engineering 12568:Computational mathematics 12545: 12492: 12454: 12401: 12363: 12325: 12267: 12184: 12130: 12092: 12037: 11974: 11907: 11871: 11828: 11792: 11725: 11714: 11644:has introductory lectures 11571:Lambda Calculi with Types 11436:10.1017/S0956796800020025 11376:"Dependent Types at Work" 10110:calculus of constructions 10021:) and axioms about sets. 10008: 9748:, and its connections to 9601:calculus of constructions 9325:propositional equivalence 5832:Parentheses indicate the 4946:is a formal variable and 4223:), notated with the type 3357:{\displaystyle A\times B} 2947:rearrange the assumptions 452:The programming language 384:calculus of constructions 345:automated theorem provers 220:calculus of constructions 193:foundation of mathematics 55:foundation of mathematics 15112:Distributional semantics 12603:Computational healthcare 12598:Differentiable computing 12517:Graphics processing unit 11936:Domain-specific language 11805:Computational complexity 11493:"Axioms and Computation" 11119:"proof by contradiction" 10598:Church demonstrated his 10556: 10437:Basic Simple Type Theory 10400:Thompson, Simon (1991). 10221:(2nd ed.). Kluwer. 10116: 10078: 9746:Curry–Howard isomorphism 8375:; this is formalized by 8369:BHK intuitionistic logic 7923:is usually defined with 4075:The interplay, known as 4069:Martin-Löf type theories 3756:constructive mathematics 3750:Constructive mathematics 3330:{\displaystyle A\land B} 2894:in the type environment 972: 908:{\displaystyle \varphi } 885:{\displaystyle \varphi } 806:Type theory with records 282:Mathematical foundations 212:constructive mathematics 143:ramified theory of types 15173:Systems of formal logic 15107:Computational semantics 14844:Subsective modification 14648:Propositional attitudes 14071:Self-verifying theories 13892:Tarski's axiomatization 12843:Tarski's undefinability 12838:incompleteness theorems 12578:Computational chemistry 12512:Photograph manipulation 12403:Artificial intelligence 12219:Decision support system 11585:notes by Per Martin-Löf 11573:book by Henk Barendregt 11497:Theorem Proving in Lean 11327:(inactive 2024-09-12). 11003:"Types of proof system" 10990:. Homotopy Type Theory. 10273:Cardelli, Luca (1996). 9725:, or more naturally as 9719:encodes numbers as sets 9437:{\displaystyle x+1=1+x} 9195:may then be written as 9086:{\displaystyle \sigma } 8424:{\displaystyle \Sigma } 7886:{\displaystyle \sqcup } 7471:{\displaystyle \sigma } 7393:{\displaystyle \times } 5432:{\displaystyle \sigma } 5005:{\displaystyle \sigma } 4779:does not have the type 4526:{\displaystyle \sigma } 4456:{\displaystyle \sigma } 3394:{\displaystyle A\lor B} 3302:Function to Empty Type 2966:for judgmental equality 2907:{\displaystyle \Gamma } 2827:{\displaystyle \Gamma } 2566:{\displaystyle \Delta } 2546:{\displaystyle \Gamma } 2385:to stress that this is 2378:{\displaystyle \equiv } 2352:{\displaystyle \Gamma } 2200:{\displaystyle \Gamma } 2074:{\displaystyle \Gamma } 1977:{\displaystyle \Gamma } 1896:{\displaystyle \Delta } 1875:{\displaystyle \Gamma } 1680:{\displaystyle \vdash } 828:computational semantics 435:static program analysis 15137:Philosophy of language 14774:Inalienable possession 14754:Free choice inferences 14749:Faultless disagreement 14520:Generalized quantifier 14445:Mathematics portal 14056:Proof of impossibility 13704:propositional variable 13014:Propositional calculus 12643:Educational technology 12474:Reinforcement learning 12224:Process control system 12122:Computational geometry 12112:Algorithmic efficiency 12107:Analysis of algorithms 11755:Systems on Chip (SoCs) 11181:Bell, John L. (2012). 10917:Cooper, Robin (2010). 10642:ISBN 978-1-78328-479-5 10571:§ Terms and types 10195:Type–token distinction 10152:others under the name 10141:others defined in the 9999: 9940: 9881: 9837: 9801: 9704: 9684: 9656:law of excluded middle 9603:with inductive types. 9550: 9524: 9489: 9469: 9438: 9400: 9374: 9348: 9303: 9189: 9160: 9140: 9087: 9067: 9016: 8954: 8917: 8897: 8844: 8824: 8773: 8750:Sum types are seen in 8741: 8704: 8684: 8647: 8627: 8522: 8502: 8465: 8425: 8405: 8337: 8313: 8241: 8217: 8147: 8033: 7975: 7917: 7887: 7867: 7827: 7807: 7752: 7732: 7679: 7604: 7532: 7512: 7492: 7472: 7452: 7426: 7394: 7374: 7304: 7274: 7254: 7204: 7184: 7183:{\displaystyle U\to U} 7158: 7125: 7101: 7056: 6999: 6951: 6917: 6886: 6864: 6842: 6806: 6786: 6760: 6740: 6720: 6698: 6662: 6642: 6616: 6592: 6570: 6543:Common terms and types 6533: 6513: 6512:{\displaystyle \beta } 6487: 6408: 6407:{\displaystyle \beta } 6385: 6365: 6345: 6325: 6305: 6266: 6246: 6226: 6206: 6186: 6147: 6127: 6103: 6083: 6036: 6035:{\displaystyle \beta } 6016: 5950: 5930: 5929:{\displaystyle \beta } 5902: 5823: 5737: 5678: 5613: 5583: 5553: 5523: 5503: 5502:{\displaystyle (t\,s)} 5473: 5453: 5433: 5413: 5393: 5367: 5315: 5269: 5239: 5203: 5173: 5151: 5066: 5046: 5026: 5006: 4986: 4960: 4940: 4920: 4873: 4841: 4773: 4745: 4699: 4669: 4585: 4547: 4527: 4503: 4477: 4457: 4421: 4381: 4344: 4293: 4250: 4217: 4183: 4148: 3983:"proofs as programs". 3976: 3928: 3908: 3888: 3868: 3852:proof by contradiction 3841: 3821: 3801: 3772: 3736: 3677: 3622: 3577: 3522: 3477: 3422: 3395: 3358: 3331: 3294: 3267: 3266:{\displaystyle \neg A} 3233: 3232:{\displaystyle A\to B} 3206: 3205:{\displaystyle A\to B} 3169: 3148: 3119: 3098: 3053:law of excluded middle 2908: 2888: 2868: 2848: 2828: 2804: 2743: 2698: 2668: 2641: 2614: 2587: 2567: 2547: 2520: 2379: 2353: 2333: 2313: 2286: 2257: 2201: 2181: 2154: 2125: 2075: 2055: 2035: 2014: 1978: 1958: 1936: 1897: 1876: 1849: 1788: 1681: 1658: 1628: 1585: 1555: 1535: 1502: 1475: 1455: 1428: 1398: 1368: 1338: 1315: 1289: 1257: 1191: 1147: 1115: 1095: 1067: 1042: 1011: 963: 909: 886: 853:Type theory as a logic 822:. It has been used in 776: 728: 696: 676: 662:from entities of type 652: 613: 587:are types, then so is 581: 561: 533: 513: 106:History of type theory 84:use a type theory for 15032:Plural quantification 14926:Inquisitive semantics 14891:Alternative semantics 14314:Kolmogorov complexity 14267:Computably enumerable 14167:Model complete theory 13959:Principia Mathematica 13019:Propositional formula 12848:Banach–Tarski paradox 12613:Electronic publishing 12583:Computational biology 12573:Computational physics 12469:Unsupervised learning 12383:Distributed computing 12259:Information retrieval 12166:Mathematical analysis 12156:Mathematical software 12039:Theory of computation 12004:Software construction 11994:Requirements analysis 11872:Software organization 11800:Computer architecture 11770:Hardware acceleration 11735:Printed circuit board 11553:Introductory material 10905:10.1093/logcom/exi004 10745:Alonzo Church (1956) 10638:Balbaert, Ivo (2015) 10503:Laan, T.D.L. (1997). 10267:categorical semantics 10236:Jacobs, Bart (1999). 10154:typed lambda calculus 10074:List of type theories 10000: 9941: 9882: 9838: 9802: 9705: 9685: 9551: 9525: 9490: 9470: 9439: 9401: 9375: 9349: 9304: 9190: 9161: 9159:{\displaystyle \tau } 9141: 9088: 9068: 9017: 8955: 8918: 8898: 8845: 8825: 8774: 8742: 8705: 8685: 8648: 8628: 8523: 8503: 8466: 8426: 8406: 8338: 8314: 8242: 8218: 8148: 8034: 7976: 7918: 7888: 7868: 7828: 7808: 7753: 7733: 7680: 7605: 7533: 7513: 7511:{\displaystyle \tau } 7493: 7473: 7453: 7432:has the product type 7427: 7425:{\displaystyle (s,t)} 7395: 7375: 7373:{\displaystyle (s,t)} 7305: 7275: 7255: 7205: 7185: 7159: 7126: 7102: 7057: 7000: 6952: 6918: 6887: 6865: 6843: 6807: 6787: 6761: 6741: 6739:{\displaystyle \ast } 6721: 6699: 6697:{\displaystyle \top } 6663: 6643: 6617: 6593: 6571: 6569:{\displaystyle \bot } 6534: 6532:{\displaystyle \eta } 6514: 6488: 6409: 6386: 6366: 6346: 6326: 6306: 6267: 6247: 6227: 6207: 6192:is applied to a term 6187: 6148: 6146:{\displaystyle \eta } 6128: 6104: 6084: 6037: 6017: 5951: 5949:{\displaystyle \eta } 5931: 5903: 5824: 5738: 5679: 5614: 5584: 5554: 5524: 5522:{\displaystyle \tau } 5504: 5474: 5454: 5434: 5414: 5394: 5368: 5316: 5270: 5240: 5204: 5174: 5152: 5067: 5047: 5045:{\displaystyle \tau } 5027: 5007: 4987: 4961: 4941: 4921: 4874: 4842: 4774: 4746: 4700: 4670: 4586: 4548: 4546:{\displaystyle \tau } 4528: 4504: 4478: 4476:{\displaystyle \tau } 4458: 4422: 4382: 4345: 4294: 4251: 4218: 4184: 4149: 3977: 3929: 3909: 3889: 3869: 3842: 3822: 3802: 3773: 3737: 3678: 3623: 3578: 3523: 3478: 3423: 3396: 3359: 3332: 3295: 3268: 3234: 3207: 3170: 3168:{\displaystyle \bot } 3149: 3147:{\displaystyle \bot } 3120: 3118:{\displaystyle \top } 3099: 3097:{\displaystyle \top } 2909: 2889: 2887:{\displaystyle \tau } 2869: 2849: 2847:{\displaystyle \tau } 2829: 2805: 2744: 2699: 2669: 2642: 2640:{\displaystyle T_{2}} 2615: 2613:{\displaystyle T_{1}} 2588: 2568: 2548: 2521: 2380: 2354: 2334: 2314: 2312:{\displaystyle t_{2}} 2287: 2285:{\displaystyle t_{1}} 2258: 2202: 2182: 2180:{\displaystyle T_{2}} 2155: 2153:{\displaystyle T_{1}} 2126: 2076: 2056: 2036: 2015: 1979: 1959: 1937: 1898: 1877: 1850: 1789: 1682: 1659: 1629: 1586: 1556: 1536: 1503: 1476: 1456: 1454:{\displaystyle t_{2}} 1429: 1427:{\displaystyle t_{1}} 1399: 1397:{\displaystyle T_{2}} 1369: 1367:{\displaystyle T_{1}} 1339: 1316: 1290: 1258: 1192: 1148: 1116: 1096: 1068: 1043: 1012: 964: 910: 887: 777: 729: 697: 677: 653: 614: 582: 562: 534: 514: 429:Programming languages 367:HOL family of provers 230:, and other computer 189:Kleene–Rosser paradox 160:Principia Mathematica 147:axiom of reducibility 15017:Function application 14824:Responsive predicate 14814:Privative adjectives 14262:Church–Turing thesis 14249:Computability theory 13458:continuum hypothesis 12976:Square of opposition 12834:Gödel's completeness 12373:Concurrent computing 12345:Ubiquitous computing 12317:Application security 12312:Information security 12141:Discrete mathematics 12117:Randomized algorithm 12069:Computability theory 12047:Model of computation 12019:Software maintenance 12014:Software engineering 11976:Software development 11926:Programming language 11921:Programming paradigm 11838:Network architecture 11656:Summer 2013 lectures 11595:Homotopy Type Theory 10337:Constable, Robert L. 10166:Homotopy type theory 10032:of the type theory. 10030:normalizing property 9950: 9891: 9847: 9811: 9775: 9765:strongly normalizing 9694: 9674: 9660:intuitionistic logic 9643:Set theory has both 9561:homotopy type theory 9534: 9499: 9479: 9448: 9410: 9384: 9358: 9338: 9327:, as opposed to the 9199: 9174: 9150: 9099: 9077: 9029: 8964: 8931: 8907: 8856: 8834: 8786: 8758: 8714: 8694: 8657: 8637: 8532: 8512: 8475: 8438: 8415: 8404:{\displaystyle \Pi } 8395: 8336:{\displaystyle g\,y} 8323: 8253: 8240:{\displaystyle f\,x} 8227: 8160: 8047: 7985: 7930: 7901: 7877: 7857: 7817: 7764: 7742: 7692: 7614: 7542: 7522: 7502: 7482: 7462: 7436: 7404: 7384: 7352: 7284: 7264: 7221: 7194: 7168: 7135: 7115: 7074: 7012: 6973: 6927: 6896: 6874: 6852: 6828: 6796: 6770: 6750: 6730: 6708: 6688: 6652: 6626: 6606: 6580: 6560: 6523: 6503: 6420: 6398: 6375: 6355: 6335: 6315: 6276: 6256: 6236: 6216: 6196: 6161: 6137: 6117: 6093: 6048: 6026: 5963: 5940: 5920: 5844: 5748: 5689: 5630: 5593: 5563: 5533: 5513: 5483: 5463: 5443: 5423: 5403: 5377: 5357: 5351:function application 5341:Function application 5279: 5249: 5213: 5183: 5163: 5078: 5056: 5036: 5016: 4996: 4970: 4950: 4930: 4895: 4855: 4783: 4755: 4709: 4681: 4597: 4567: 4537: 4517: 4487: 4467: 4447: 4392: 4355: 4304: 4267: 4227: 4193: 4162: 4128: 4092:Homotopy type theory 4088:Homotopy type theory 4083:Homotopy type theory 3975:{\displaystyle \to } 3966: 3918: 3898: 3878: 3858: 3831: 3811: 3800:{\displaystyle P(x)} 3782: 3762: 3687: 3640: 3588: 3543: 3488: 3443: 3406: 3379: 3342: 3315: 3278: 3254: 3217: 3190: 3159: 3138: 3109: 3088: 3049:intuitionistic logic 3031:Intuitionistic logic 3001:Homotopy Type Theory 2898: 2878: 2858: 2838: 2818: 2770: 2737: 2708: 2678: 2658: 2624: 2597: 2577: 2557: 2537: 2421: 2369: 2343: 2323: 2296: 2269: 2215: 2191: 2164: 2137: 2089: 2065: 2045: 2025: 1992: 1968: 1948: 1920: 1887: 1866: 1802: 1693: 1671: 1638: 1595: 1565: 1545: 1512: 1492: 1465: 1438: 1411: 1381: 1351: 1328: 1305: 1279: 1201: 1157: 1125: 1105: 1080: 1075:conditional operator 1055: 1021: 1017:, the Boolean value 1001: 995:function application 923: 899: 876: 742: 706: 686: 682:to entities of type 666: 630: 591: 571: 551: 539:for individuals and 523: 503: 300:homotopy type theory 236:homotopy type theory 126:(first described in 15102:Cognitive semantics 15067:Strawson entailment 15012:Existential closure 14956:Situation semantics 14859:Temperature paradox 14829:Rising declaratives 14794:Modal subordination 14769:Hurford disjunction 14729:Discourse relations 14416:Mathematical object 14307:P versus NP problem 14272:Computable function 14066:Reverse mathematics 13992:Logical consequence 13869:primitive recursive 13864:elementary function 13637:Free/bound variable 13490:Tarski–Grothendieck 13009:Logical connectives 12939:Logical equivalence 12789:Logical consequence 12648:Document management 12638:Operations research 12563:Enterprise software 12479:Multi-task learning 12464:Supervised learning 12186:Information systems 12009:Software deployment 11966:Software repository 11820:Real-time computing 11672:Andrej Bauer's blog 11559:Type Theory at nLab 11462:Milewski, Bartosz. 10881:(2):159--219 (1981) 10651:docs.julialang.org 10172:Cubical Type Theory 10112:and its derivatives 10044:cubical type theory 9578:induction-induction 9574:induction-recursion 9549:{\displaystyle t=t} 9399:{\displaystyle 1+x} 9373:{\displaystyle x+1} 8508:and a term of type 8471:, which takes in a 8349:logical disjunction 7839:logical conjunction 7380:or with the symbol 5834:order of operations 4441:defined inductively 4100:cubical type theory 3421:{\displaystyle A+B} 2387:judgmental equality 2187:(under assumptions 2061:(under assumptions 983:recursively defined 917:well-formed formula 857:A type theory is a 736:indicator functions 482:categorial grammars 40:formal presentation 15147:Semantics of logic 15072:Strict conditional 15042:Quantifier raising 15007:Downward entailing 14987:Autonomy of syntax 14916:Generative grammar 14896:Categorial grammar 14834:Scalar implicature 14739:Epistemic modality 14714:De dicto and de re 14214:Transfer principle 14177:Semantics of logic 14162:Categorical theory 14138:Non-standard model 13652:Logical connective 12779:Information theory 12728:Mathematical logic 12431:Search methodology 12378:Parallel computing 12335:Interaction design 12244:Computing platform 12171:Numerical analysis 12161:Information theory 11946:Software framework 11909:Software notations 11848:Network components 11745:Integrated circuit 11642:2005 summer school 10956:10.1007/BF00484985 10858:2022-05-10 at the 10658:2022-03-24 at the 10547:Montague Semantics 10458:2011-06-07 at the 10406:. Addison–Wesley. 10185:Class (set theory) 10089:higher-order logic 9995: 9936: 9877: 9833: 9797: 9742:BHK interpretation 9700: 9680: 9668:predicate function 9546: 9520: 9485: 9465: 9434: 9396: 9370: 9354:. For example, if 9344: 9299: 9185: 9156: 9136: 9083: 9063: 9012: 8950: 8913: 8893: 8840: 8820: 8769: 8737: 8700: 8680: 8643: 8623: 8518: 8498: 8461: 8421: 8401: 8333: 8309: 8237: 8213: 8143: 8029: 7971: 7913: 7883: 7863: 7823: 7803: 7748: 7728: 7675: 7600: 7528: 7508: 7488: 7468: 7448: 7422: 7390: 7370: 7300: 7280:is a term of type 7270: 7250: 7200: 7180: 7154: 7121: 7097: 7052: 7007:successor function 6995: 6947: 6913: 6882: 6860: 6838: 6802: 6782: 6756: 6736: 6716: 6694: 6658: 6638: 6612: 6588: 6566: 6529: 6509: 6483: 6404: 6381: 6361: 6341: 6321: 6301: 6262: 6242: 6222: 6202: 6182: 6143: 6123: 6099: 6079: 6032: 6012: 5946: 5926: 5898: 5819: 5733: 5674: 5609: 5579: 5549: 5519: 5499: 5469: 5449: 5429: 5419:is a term of type 5409: 5389: 5373:is a term of type 5363: 5330:anonymous function 5311: 5265: 5235: 5199: 5169: 5147: 5062: 5042: 5022: 5002: 4982: 4956: 4936: 4916: 4889:lambda expressions 4869: 4837: 4769: 4741: 4695: 4665: 4581: 4543: 4523: 4499: 4473: 4453: 4417: 4377: 4340: 4289: 4246: 4213: 4179: 4144: 3972: 3924: 3904: 3884: 3864: 3837: 3817: 3797: 3768: 3732: 3673: 3618: 3573: 3530:Dependent Product 3518: 3473: 3418: 3391: 3354: 3327: 3290: 3263: 3229: 3202: 3165: 3144: 3115: 3094: 2904: 2884: 2864: 2844: 2824: 2800: 2739: 2736: 2694: 2664: 2637: 2610: 2583: 2563: 2543: 2516: 2514: 2397:Rules of Inference 2375: 2349: 2329: 2309: 2282: 2253: 2197: 2177: 2150: 2121: 2071: 2051: 2041:is a term of type 2031: 2010: 1974: 1954: 1932: 1893: 1872: 1845: 1784: 1677: 1654: 1634:is a term of type 1624: 1591:, it follows that 1581: 1561:is a term of type 1551: 1531: 1508:is a term of type 1498: 1471: 1451: 1424: 1394: 1364: 1334: 1311: 1285: 1253: 1187: 1143: 1111: 1091: 1063: 1050:successor function 1038: 1007: 959: 905: 892:is true", or "The 882: 863:rules of inference 859:mathematical logic 802:and Cooper 1981). 772: 724: 692: 672: 648: 609: 577: 557: 529: 509: 496:, etc.) of words. 363:higher-order logic 315:algebraic topology 261:. You can help by 197:higher-order logic 88:. A common one is 15155: 15154: 15127:Logic translation 15090: 15089: 15082:Universal grinder 15062:Squiggle operator 15022:Meaning postulate 14961:Supervaluationism 14931:Intensional logic 14911:Dynamic semantics 14872: 14871: 14704:Crossover effects 14653:Tense–aspect–mood 14633:Lexical semantics 14452: 14451: 14384:Abstract category 14187:Theories of truth 13997:Rule of inference 13987:Natural deduction 13968: 13967: 13513: 13512: 13218:Cartesian product 13123: 13122: 13029:Many-valued logic 13004:Boolean functions 12887:Russell's paradox 12862:diagonal argument 12759:First-order logic 12694: 12693: 12623:Electronic voting 12553:Quantum Computing 12546:Applied computing 12532:Image compression 12302:Hardware security 12292:Security services 12249:Digital marketing 12029:Open-source model 11941:Modeling language 11853:Network scheduler 11602:Advanced material 11397:978-3-642-03153-3 11260:978-1-6654-4895-6 11199:978-0-08-093066-4 11167:978-3-319-47165-5 11066:978-0-521-76614-2 10827:978-0-7486-7777-1 10789:978-3-319-50422-3 10617:(x,y) -> x^5+y 10495:978-3-7643-8349-7 10446:978-0-521-05422-5 10433:Hindley, J. Roger 10326:978-3-8473-2963-3 10249:978-0-444-50170-7 10228:978-1-4020-0763-7 10147:pure type systems 10137:combinatory logic 10019:first-order logic 9703:{\displaystyle x} 9683:{\displaystyle x} 9617:first-order logic 9488:{\displaystyle t} 9347:{\displaystyle =} 9267: 8916:{\displaystyle y} 8843:{\displaystyle x} 8703:{\displaystyle a} 8646:{\displaystyle a} 8521:{\displaystyle a} 8365:type dependencies 7866:{\displaystyle +} 7826:{\displaystyle t} 7751:{\displaystyle s} 7531:{\displaystyle t} 7491:{\displaystyle s} 7273:{\displaystyle n} 7203:{\displaystyle U} 7124:{\displaystyle a} 6835: 6805:{\displaystyle a} 6759:{\displaystyle a} 6661:{\displaystyle a} 6615:{\displaystyle a} 6600:type inhabitation 6384:{\displaystyle t} 6364:{\displaystyle t} 6344:{\displaystyle v} 6324:{\displaystyle t} 6265:{\displaystyle s} 6245:{\displaystyle t} 6225:{\displaystyle v} 6205:{\displaystyle s} 6126:{\displaystyle t} 6102:{\displaystyle v} 5895: 5816: 5730: 5671: 5661: 5606: 5576: 5546: 5472:{\displaystyle s} 5452:{\displaystyle t} 5412:{\displaystyle s} 5366:{\displaystyle t} 5172:{\displaystyle x} 5065:{\displaystyle t} 5025:{\displaystyle v} 4959:{\displaystyle t} 4939:{\displaystyle v} 4849:right associative 4077:categorical logic 3996:program synthesis 3927:{\displaystyle x} 3907:{\displaystyle x} 3887:{\displaystyle x} 3867:{\displaystyle x} 3840:{\displaystyle P} 3820:{\displaystyle x} 3771:{\displaystyle x} 3634: 3633: 3025:computer programs 2867:{\displaystyle t} 2764:type inhabitation 2758:Type inhabitation 2752:Type inhabitation 2667:{\displaystyle 0} 2586:{\displaystyle t} 2363: 2362: 2332:{\displaystyle T} 2319:are both of type 2160:is equal to type 2054:{\displaystyle T} 2034:{\displaystyle t} 1957:{\displaystyle T} 1750: 1554:{\displaystyle y} 1501:{\displaystyle x} 1474:{\displaystyle T} 1337:{\displaystyle T} 1314:{\displaystyle t} 1288:{\displaystyle T} 1114:{\displaystyle 0} 1010:{\displaystyle 0} 820:type theory types 695:{\displaystyle b} 675:{\displaystyle a} 580:{\displaystyle b} 560:{\displaystyle a} 532:{\displaystyle t} 512:{\displaystyle e} 486:pregroup grammars 474:natural languages 439:semantic analysis 279: 278: 145:together with an 124:Russell's paradox 15185: 15132:Linguistics wars 15057:Semantic parsing 14946:Montague grammar 14881: 14880: 14724:Deontic modality 14578: 14577: 14565:Truth conditions 14500:Compositionality 14493:Central concepts 14479: 14472: 14465: 14456: 14455: 14443: 14442: 14394:History of logic 14389:Category of sets 14282:Decision problem 14061:Ordinal analysis 14002:Sequent calculus 13900:Boolean algebras 13840: 13839: 13814: 13785:logical/constant 13539: 13538: 13525: 13448:Zermelo–Fraenkel 13199:Set operations: 13134: 13133: 13071: 12902: 12901: 12882:Löwenheim–Skolem 12769:Formal semantics 12721: 12714: 12707: 12698: 12697: 12684: 12683: 12674: 12673: 12664: 12663: 12484:Cross-validation 12456:Machine learning 12340:Social computing 12307:Network security 12102:Algorithm design 12024:Programming team 11984:Control variable 11961:Software library 11899:Software quality 11894:Operating system 11843:Network protocol 11708:Computer science 11701: 11694: 11687: 11678: 11677: 11619: 11542: 11541: 11539: 11538: 11519: 11513: 11512: 11510: 11508: 11489: 11483: 11482: 11480: 11479: 11459: 11450: 11449: 11447: 11413: 11407: 11406: 11405: 11404: 11371: 11362: 11356: 11350: 11349: 11343: 11335: 11333: 11326: 11316: 11302: 11293: 11284: 11283: 11281: 11280: 11244: 11224: 11218: 11217: 11215: 11214: 11208: 11187: 11178: 11172: 11171: 11145: 11139: 11138: 11136: 11134: 11115: 11109: 11108: 11106: 11105: 11099: 11092: 11084: 11071: 11070: 11050: 11029: 11028: 11026: 11024: 11018: 11010:logicmatters.net 11007: 10998: 10992: 10991: 10981: 10968: 10967: 10935: 10926: 10915: 10909: 10908: 10888: 10882: 10869: 10863: 10851:Cooper, Robin. " 10849: 10843: 10842: 10840: 10839: 10811: 10805: 10804: 10802: 10801: 10773: 10767: 10755: 10749: 10743: 10737: 10736: 10697: 10684: 10668: 10662: 10649: 10643: 10636: 10620: 10618: 10609: 10603: 10596: 10590: 10579: 10573: 10567: 10538: 10536: 10518:10.6100/IR498552 10511: 10499: 10480: 10450: 10428: 10426: 10425: 10396: 10383:Coquand, Thierry 10376:Naïve Set Theory 10368: 10366: 10345: 10330: 10303: 10301: 10300: 10264: 10262: 10261: 10232: 10213: 10004: 10002: 10001: 9996: 9994: 9993: 9984: 9983: 9968: 9967: 9945: 9943: 9942: 9937: 9935: 9934: 9922: 9921: 9909: 9908: 9886: 9884: 9883: 9878: 9876: 9875: 9866: 9865: 9856: 9855: 9842: 9840: 9839: 9834: 9820: 9819: 9806: 9804: 9803: 9798: 9784: 9783: 9709: 9707: 9706: 9701: 9689: 9687: 9686: 9681: 9589:proof assistants 9555: 9553: 9552: 9547: 9529: 9527: 9526: 9521: 9515: 9494: 9492: 9491: 9486: 9474: 9472: 9471: 9466: 9464: 9443: 9441: 9440: 9435: 9406:are terms, then 9405: 9403: 9402: 9397: 9379: 9377: 9376: 9371: 9353: 9351: 9350: 9345: 9308: 9306: 9305: 9300: 9280: 9269: 9268: 9234: 9233: 9194: 9192: 9191: 9186: 9184: 9165: 9163: 9162: 9157: 9145: 9143: 9142: 9137: 9127: 9109: 9092: 9090: 9089: 9084: 9072: 9070: 9069: 9064: 9054: 9039: 9021: 9019: 9018: 9013: 8993: 8992: 8974: 8959: 8957: 8956: 8951: 8949: 8948: 8922: 8920: 8919: 8914: 8902: 8900: 8899: 8894: 8884: 8866: 8849: 8847: 8846: 8841: 8829: 8827: 8826: 8821: 8811: 8796: 8778: 8776: 8775: 8770: 8768: 8746: 8744: 8743: 8738: 8732: 8731: 8709: 8707: 8706: 8701: 8689: 8687: 8686: 8681: 8675: 8674: 8652: 8650: 8649: 8644: 8632: 8630: 8629: 8624: 8615: 8614: 8586: 8585: 8554: 8527: 8525: 8524: 8519: 8507: 8505: 8504: 8499: 8493: 8492: 8470: 8468: 8467: 8462: 8460: 8430: 8428: 8427: 8422: 8410: 8408: 8407: 8402: 8342: 8340: 8339: 8334: 8318: 8316: 8315: 8310: 8301: 8272: 8246: 8244: 8243: 8238: 8222: 8220: 8219: 8214: 8205: 8179: 8152: 8150: 8149: 8144: 8066: 8038: 8036: 8035: 8030: 8004: 7980: 7978: 7977: 7972: 7946: 7922: 7920: 7919: 7914: 7892: 7890: 7889: 7884: 7872: 7870: 7869: 7864: 7832: 7830: 7829: 7824: 7812: 7810: 7809: 7804: 7786: 7757: 7755: 7754: 7749: 7737: 7735: 7734: 7729: 7711: 7684: 7682: 7681: 7676: 7636: 7609: 7607: 7606: 7601: 7561: 7537: 7535: 7534: 7529: 7517: 7515: 7514: 7509: 7497: 7495: 7494: 7489: 7477: 7475: 7474: 7469: 7457: 7455: 7454: 7449: 7431: 7429: 7428: 7423: 7399: 7397: 7396: 7391: 7379: 7377: 7376: 7371: 7327:Girard's Paradox 7309: 7307: 7306: 7301: 7299: 7298: 7279: 7277: 7276: 7271: 7259: 7257: 7256: 7251: 7245: 7244: 7209: 7207: 7206: 7201: 7189: 7187: 7186: 7181: 7163: 7161: 7160: 7155: 7153: 7152: 7131:. In this case, 7130: 7128: 7127: 7122: 7106: 7104: 7103: 7098: 7092: 7091: 7066:Dependent typing 7061: 7059: 7058: 7053: 7051: 7050: 7035: 7034: 7019: 7004: 7002: 7001: 6996: 6994: 6993: 6967:Peano Arithmetic 6956: 6954: 6953: 6948: 6946: 6922: 6920: 6919: 6914: 6912: 6891: 6889: 6888: 6883: 6881: 6869: 6867: 6866: 6861: 6859: 6847: 6845: 6844: 6839: 6837: 6836: 6811: 6809: 6808: 6803: 6791: 6789: 6788: 6783: 6765: 6763: 6762: 6757: 6745: 6743: 6742: 6737: 6725: 6723: 6722: 6717: 6715: 6703: 6701: 6700: 6695: 6667: 6665: 6664: 6659: 6647: 6645: 6644: 6639: 6621: 6619: 6618: 6613: 6602:. If for a type 6597: 6595: 6594: 6589: 6587: 6575: 6573: 6572: 6567: 6538: 6536: 6535: 6530: 6518: 6516: 6515: 6510: 6492: 6490: 6489: 6484: 6474: 6445: 6413: 6411: 6410: 6405: 6390: 6388: 6387: 6382: 6370: 6368: 6367: 6362: 6350: 6348: 6347: 6342: 6330: 6328: 6327: 6322: 6310: 6308: 6307: 6302: 6271: 6269: 6268: 6263: 6251: 6249: 6248: 6243: 6231: 6229: 6228: 6223: 6211: 6209: 6208: 6203: 6191: 6189: 6188: 6183: 6152: 6150: 6149: 6144: 6132: 6130: 6129: 6124: 6108: 6106: 6105: 6100: 6088: 6086: 6085: 6080: 6041: 6039: 6038: 6033: 6021: 6019: 6018: 6013: 5955: 5953: 5952: 5947: 5935: 5933: 5932: 5927: 5907: 5905: 5904: 5899: 5897: 5896: 5876: 5857: 5838:left associative 5828: 5826: 5825: 5820: 5818: 5817: 5791: 5767: 5742: 5740: 5739: 5734: 5732: 5731: 5708: 5683: 5681: 5680: 5675: 5673: 5672: 5663: 5662: 5646: 5618: 5616: 5615: 5610: 5608: 5607: 5588: 5586: 5585: 5580: 5578: 5577: 5558: 5556: 5555: 5550: 5548: 5547: 5528: 5526: 5525: 5520: 5508: 5506: 5505: 5500: 5479:, often written 5478: 5476: 5475: 5470: 5458: 5456: 5455: 5450: 5438: 5436: 5435: 5430: 5418: 5416: 5415: 5410: 5398: 5396: 5395: 5390: 5372: 5370: 5369: 5364: 5320: 5318: 5317: 5312: 5310: 5309: 5294: 5293: 5274: 5272: 5271: 5266: 5264: 5263: 5244: 5242: 5241: 5236: 5226: 5208: 5206: 5205: 5200: 5198: 5197: 5178: 5176: 5175: 5170: 5159:The variable is 5156: 5154: 5153: 5148: 5146: 5145: 5130: 5129: 5103: 5071: 5069: 5068: 5063: 5051: 5049: 5048: 5043: 5031: 5029: 5028: 5023: 5011: 5009: 5008: 5003: 4991: 4989: 4988: 4983: 4965: 4963: 4962: 4957: 4945: 4943: 4942: 4937: 4925: 4923: 4922: 4917: 4878: 4876: 4875: 4870: 4868: 4846: 4844: 4843: 4838: 4836: 4835: 4817: 4816: 4801: 4800: 4778: 4776: 4775: 4770: 4768: 4750: 4748: 4747: 4742: 4740: 4739: 4724: 4723: 4704: 4702: 4701: 4696: 4694: 4674: 4672: 4671: 4666: 4661: 4660: 4645: 4644: 4626: 4625: 4610: 4590: 4588: 4587: 4582: 4580: 4552: 4550: 4549: 4544: 4532: 4530: 4529: 4524: 4508: 4506: 4505: 4500: 4482: 4480: 4479: 4474: 4462: 4460: 4459: 4454: 4426: 4424: 4423: 4418: 4416: 4415: 4386: 4384: 4383: 4378: 4376: 4375: 4349: 4347: 4346: 4341: 4339: 4338: 4320: 4298: 4296: 4295: 4290: 4288: 4287: 4258:formal variables 4255: 4253: 4252: 4247: 4245: 4244: 4222: 4220: 4219: 4214: 4212: 4188: 4186: 4185: 4180: 4178: 4153: 4151: 4150: 4145: 4143: 4142: 3981: 3979: 3978: 3973: 3933: 3931: 3930: 3925: 3913: 3911: 3910: 3905: 3893: 3891: 3890: 3885: 3873: 3871: 3870: 3865: 3846: 3844: 3843: 3838: 3826: 3824: 3823: 3818: 3806: 3804: 3803: 3798: 3777: 3775: 3774: 3769: 3741: 3739: 3738: 3733: 3682: 3680: 3679: 3674: 3627: 3625: 3624: 3619: 3582: 3580: 3579: 3574: 3527: 3525: 3524: 3519: 3482: 3480: 3479: 3474: 3427: 3425: 3424: 3419: 3400: 3398: 3397: 3392: 3363: 3361: 3360: 3355: 3336: 3334: 3333: 3328: 3299: 3297: 3296: 3291: 3272: 3270: 3269: 3264: 3238: 3236: 3235: 3230: 3211: 3209: 3208: 3203: 3174: 3172: 3171: 3166: 3153: 3151: 3150: 3145: 3124: 3122: 3121: 3116: 3103: 3101: 3100: 3095: 3065: 3064: 2919:Girard's paradox 2913: 2911: 2910: 2905: 2893: 2891: 2890: 2885: 2873: 2871: 2870: 2865: 2853: 2851: 2850: 2845: 2833: 2831: 2830: 2825: 2814:Given a context 2809: 2807: 2806: 2801: 2748: 2746: 2745: 2740: 2738: 2703: 2701: 2700: 2695: 2693: 2692: 2673: 2671: 2670: 2665: 2646: 2644: 2643: 2638: 2636: 2635: 2619: 2617: 2616: 2611: 2609: 2608: 2592: 2590: 2589: 2584: 2572: 2570: 2569: 2564: 2552: 2550: 2549: 2544: 2525: 2523: 2522: 2517: 2515: 2511: 2510: 2479: 2478: 2466: 2465: 2449: 2448: 2401:A type theory's 2384: 2382: 2381: 2376: 2358: 2356: 2355: 2350: 2338: 2336: 2335: 2330: 2318: 2316: 2315: 2310: 2308: 2307: 2291: 2289: 2288: 2283: 2281: 2280: 2262: 2260: 2259: 2254: 2246: 2245: 2233: 2232: 2206: 2204: 2203: 2198: 2186: 2184: 2183: 2178: 2176: 2175: 2159: 2157: 2156: 2151: 2149: 2148: 2130: 2128: 2127: 2122: 2120: 2119: 2107: 2106: 2080: 2078: 2077: 2072: 2060: 2058: 2057: 2052: 2040: 2038: 2037: 2032: 2019: 2017: 2016: 2011: 1983: 1981: 1980: 1975: 1963: 1961: 1960: 1955: 1941: 1939: 1938: 1933: 1906: 1905: 1902: 1900: 1899: 1894: 1881: 1879: 1878: 1873: 1854: 1852: 1851: 1846: 1844: 1843: 1828: 1827: 1812: 1793: 1791: 1790: 1785: 1783: 1782: 1752: 1751: 1748: 1739: 1738: 1717: 1716: 1686: 1684: 1683: 1678: 1666:turnstile symbol 1663: 1661: 1660: 1655: 1653: 1652: 1633: 1631: 1630: 1625: 1608: 1590: 1588: 1587: 1582: 1580: 1579: 1560: 1558: 1557: 1552: 1540: 1538: 1537: 1532: 1530: 1529: 1507: 1505: 1504: 1499: 1480: 1478: 1477: 1472: 1460: 1458: 1457: 1452: 1450: 1449: 1433: 1431: 1430: 1425: 1423: 1422: 1403: 1401: 1400: 1395: 1393: 1392: 1373: 1371: 1370: 1365: 1363: 1362: 1343: 1341: 1340: 1335: 1320: 1318: 1317: 1312: 1294: 1292: 1291: 1286: 1262: 1260: 1259: 1254: 1242: 1229: 1214: 1196: 1194: 1193: 1188: 1176: 1167: 1152: 1150: 1149: 1144: 1135: 1120: 1118: 1117: 1112: 1100: 1098: 1097: 1092: 1090: 1072: 1070: 1069: 1064: 1062: 1047: 1045: 1044: 1039: 1037: 1016: 1014: 1013: 1008: 968: 966: 965: 960: 958: 957: 939: 914: 912: 911: 906: 891: 889: 888: 883: 832:dialogue systems 810:formal semantics 781: 779: 778: 773: 733: 731: 730: 725: 701: 699: 698: 693: 681: 679: 678: 673: 657: 655: 654: 649: 618: 616: 615: 610: 586: 584: 583: 578: 566: 564: 563: 558: 538: 536: 535: 530: 518: 516: 515: 510: 478:Montague grammar 365:are used by the 341:proof assistants 325:Proof assistants 274: 271: 253: 246: 232:proof assistants 136:Bertrand Russell 116:naive set theory 86:their foundation 62:Typed λ-calculus 15193: 15192: 15188: 15187: 15186: 15184: 15183: 15182: 15158: 15157: 15156: 15151: 15086: 14975: 14936:Lambda calculus 14868: 14839:Sloppy identity 14799:Opaque contexts 14734:Donkey anaphora 14699:Counterfactuals 14667: 14569: 14488: 14483: 14453: 14448: 14437: 14430: 14375:Category theory 14365:Algebraic logic 14348: 14319:Lambda calculus 14257:Church encoding 14243: 14219:Truth predicate 14075: 14041:Complete theory 13964: 13833: 13829: 13825: 13820: 13812: 13532: and  13528: 13523: 13509: 13485:New Foundations 13453:axiom of choice 13436: 13398:Gödel numbering 13338: and  13330: 13234: 13119: 13069: 13050: 12999:Boolean algebra 12985: 12949:Equiconsistency 12914:Classical logic 12891: 12872:Halting problem 12860: and  12836: and  12824: and  12823: 12818:Theorems ( 12813: 12730: 12725: 12695: 12690: 12681: 12652: 12633:Word processing 12541: 12527:Virtual reality 12488: 12450: 12421:Computer vision 12397: 12393:Multiprocessing 12359: 12321: 12287:Security hacker 12263: 12239:Digital library 12180: 12131:Mathematics of 12126: 12088: 12064:Automata theory 12059:Formal language 12033: 11999:Software design 11970: 11903: 11889:Virtual machine 11867: 11863:Network service 11824: 11815:Embedded system 11788: 11721: 11710: 11705: 11623:The TYPES Forum 11604: 11555: 11550: 11545: 11536: 11534: 11521: 11520: 11516: 11506: 11504: 11491: 11490: 11486: 11477: 11475: 11460: 11453: 11414: 11410: 11402: 11400: 11398: 11372: 11365: 11357: 11353: 11337: 11336: 11331: 11300: 11294: 11287: 11278: 11276: 11261: 11225: 11221: 11212: 11210: 11206: 11200: 11185: 11179: 11175: 11168: 11146: 11142: 11132: 11130: 11117: 11116: 11112: 11103: 11101: 11097: 11090: 11086: 11085: 11074: 11067: 11051: 11032: 11022: 11020: 11016: 11005: 10999: 10995: 10982: 10971: 10936: 10929: 10916: 10912: 10889: 10885: 10870: 10866: 10860:Wayback Machine 10850: 10846: 10837: 10835: 10828: 10812: 10808: 10799: 10797: 10790: 10774: 10770: 10756: 10752: 10744: 10740: 10717:10.2307/2266170 10698: 10687: 10681:Wayback Machine 10669: 10665: 10660:Wayback Machine 10650: 10646: 10637: 10633: 10629: 10624: 10623: 10616: 10610: 10606: 10600:logistic method 10597: 10593: 10580: 10576: 10568: 10564: 10559: 10554: 10534: 10528: 10509: 10496: 10477: 10460:Wayback Machine 10447: 10423: 10421: 10414: 10364: 10358: 10343: 10327: 10298: 10296: 10289: 10259: 10257: 10250: 10229: 10203: 10201:Further reading 10181: 10162: 10160:Active research 10145:(also known as 10119: 10081: 10076: 10059:Axiom of Choice 10051:classical logic 10011: 9989: 9985: 9979: 9975: 9957: 9953: 9951: 9948: 9947: 9930: 9926: 9917: 9913: 9898: 9894: 9892: 9889: 9888: 9871: 9870: 9861: 9860: 9851: 9850: 9848: 9845: 9844: 9815: 9814: 9812: 9809: 9808: 9779: 9778: 9776: 9773: 9772: 9758: 9750:Category theory 9727:inductive types 9723:Church encoding 9695: 9692: 9691: 9675: 9672: 9671: 9633:axiom of choice 9609: 9569: 9567:Inductive types 9535: 9532: 9531: 9502: 9500: 9497: 9496: 9480: 9477: 9476: 9451: 9449: 9446: 9445: 9411: 9408: 9407: 9385: 9382: 9381: 9359: 9356: 9355: 9339: 9336: 9335: 9317: 9273: 9264: 9263: 9220: 9219: 9200: 9197: 9196: 9177: 9175: 9172: 9171: 9151: 9148: 9147: 9111: 9102: 9100: 9097: 9096: 9078: 9075: 9074: 9041: 9032: 9030: 9027: 9026: 8979: 8978: 8967: 8965: 8962: 8961: 8935: 8934: 8932: 8929: 8928: 8908: 8905: 8904: 8868: 8859: 8857: 8854: 8853: 8835: 8832: 8831: 8798: 8789: 8787: 8784: 8783: 8761: 8759: 8756: 8755: 8752:dependent pairs 8718: 8717: 8715: 8712: 8711: 8710:, and return a 8695: 8692: 8691: 8661: 8660: 8658: 8655: 8654: 8638: 8635: 8634: 8601: 8600: 8572: 8571: 8535: 8533: 8530: 8529: 8513: 8510: 8509: 8479: 8478: 8476: 8473: 8472: 8441: 8439: 8436: 8435: 8416: 8413: 8412: 8396: 8393: 8392: 8361: 8324: 8321: 8320: 8285: 8256: 8254: 8251: 8250: 8228: 8225: 8224: 8192: 8163: 8161: 8158: 8157: 8050: 8048: 8045: 8044: 7988: 7986: 7983: 7982: 7933: 7931: 7928: 7927: 7902: 7899: 7898: 7878: 7875: 7874: 7858: 7855: 7854: 7851: 7818: 7815: 7814: 7767: 7765: 7762: 7761: 7743: 7740: 7739: 7695: 7693: 7690: 7689: 7617: 7615: 7612: 7611: 7545: 7543: 7540: 7539: 7523: 7520: 7519: 7518:is the type of 7503: 7500: 7499: 7483: 7480: 7479: 7478:is the type of 7463: 7460: 7459: 7437: 7434: 7433: 7405: 7402: 7401: 7385: 7382: 7381: 7353: 7350: 7349: 7343: 7333:introduced the 7329:. The logician 7288: 7287: 7285: 7282: 7281: 7265: 7262: 7261: 7225: 7224: 7222: 7219: 7218: 7195: 7192: 7191: 7169: 7166: 7165: 7139: 7138: 7136: 7133: 7132: 7116: 7113: 7112: 7078: 7077: 7075: 7072: 7071: 7068: 7040: 7039: 7024: 7023: 7015: 7013: 7010: 7009: 6983: 6982: 6974: 6971: 6970: 6963: 6961:Natural numbers 6930: 6928: 6925: 6924: 6899: 6897: 6894: 6893: 6877: 6875: 6872: 6871: 6855: 6853: 6850: 6849: 6832: 6831: 6829: 6826: 6825: 6822: 6797: 6794: 6793: 6771: 6768: 6767: 6751: 6748: 6747: 6731: 6728: 6727: 6711: 6709: 6706: 6705: 6689: 6686: 6685: 6678: 6653: 6650: 6649: 6627: 6624: 6623: 6607: 6604: 6603: 6583: 6581: 6578: 6577: 6561: 6558: 6557: 6550: 6545: 6524: 6521: 6520: 6504: 6501: 6500: 6464: 6435: 6421: 6418: 6417: 6399: 6396: 6395: 6376: 6373: 6372: 6356: 6353: 6352: 6336: 6333: 6332: 6316: 6313: 6312: 6277: 6274: 6273: 6257: 6254: 6253: 6237: 6234: 6233: 6217: 6214: 6213: 6197: 6194: 6193: 6162: 6159: 6158: 6138: 6135: 6134: 6118: 6115: 6114: 6094: 6091: 6090: 6049: 6046: 6045: 6027: 6024: 6023: 5964: 5961: 5960: 5941: 5938: 5937: 5936:-reduction and 5921: 5918: 5917: 5914: 5892: 5891: 5866: 5847: 5845: 5842: 5841: 5813: 5812: 5781: 5757: 5749: 5746: 5745: 5727: 5726: 5698: 5690: 5687: 5686: 5668: 5667: 5658: 5657: 5636: 5631: 5628: 5627: 5603: 5602: 5594: 5591: 5590: 5573: 5572: 5564: 5561: 5560: 5543: 5542: 5534: 5531: 5530: 5514: 5511: 5510: 5484: 5481: 5480: 5464: 5461: 5460: 5444: 5441: 5440: 5424: 5421: 5420: 5404: 5401: 5400: 5378: 5375: 5374: 5358: 5355: 5354: 5347:inference rules 5343: 5338: 5336:Inference Rules 5299: 5298: 5283: 5282: 5280: 5277: 5276: 5253: 5252: 5250: 5247: 5246: 5216: 5214: 5211: 5210: 5187: 5186: 5184: 5181: 5180: 5164: 5161: 5160: 5135: 5134: 5119: 5118: 5093: 5079: 5076: 5075: 5057: 5054: 5053: 5052:is the type of 5037: 5034: 5033: 5017: 5014: 5013: 5012:is the type of 4997: 4994: 4993: 4971: 4968: 4967: 4951: 4948: 4947: 4931: 4928: 4927: 4896: 4893: 4892: 4885: 4858: 4856: 4853: 4852: 4825: 4824: 4806: 4805: 4790: 4789: 4784: 4781: 4780: 4758: 4756: 4753: 4752: 4729: 4728: 4713: 4712: 4710: 4707: 4706: 4684: 4682: 4679: 4678: 4650: 4649: 4634: 4633: 4615: 4614: 4600: 4598: 4595: 4594: 4570: 4568: 4565: 4564: 4538: 4535: 4534: 4518: 4515: 4514: 4488: 4485: 4484: 4468: 4465: 4464: 4448: 4445: 4444: 4433: 4402: 4401: 4393: 4390: 4389: 4365: 4364: 4356: 4353: 4352: 4325: 4324: 4307: 4305: 4302: 4301: 4277: 4276: 4268: 4265: 4264: 4231: 4230: 4228: 4225: 4224: 4196: 4194: 4191: 4190: 4165: 4163: 4160: 4159: 4132: 4131: 4129: 4126: 4125: 4122:natural numbers 4118: 4113: 4111:Terms and types 4108: 4085: 4027:Category theory 4023: 4021:Category theory 4018: 4010: 4004: 3967: 3964: 3963: 3956: 3919: 3916: 3915: 3899: 3896: 3895: 3879: 3876: 3875: 3859: 3856: 3855: 3832: 3829: 3828: 3812: 3809: 3808: 3783: 3780: 3779: 3763: 3760: 3759: 3752: 3688: 3685: 3684: 3641: 3638: 3637: 3589: 3586: 3585: 3544: 3541: 3540: 3489: 3486: 3485: 3444: 3441: 3440: 3407: 3404: 3403: 3380: 3377: 3376: 3343: 3340: 3339: 3316: 3313: 3312: 3279: 3276: 3275: 3255: 3252: 3251: 3218: 3215: 3214: 3191: 3188: 3187: 3160: 3157: 3156: 3139: 3136: 3135: 3110: 3107: 3106: 3089: 3086: 3085: 3057:double negation 3045:classical logic 3041:Boolean algebra 3033: 3021:category theory 3009: 2899: 2896: 2895: 2879: 2876: 2875: 2859: 2856: 2855: 2839: 2836: 2835: 2819: 2816: 2815: 2771: 2768: 2767: 2760: 2754: 2735: 2734: 2711: 2709: 2706: 2705: 2682: 2681: 2679: 2676: 2675: 2659: 2656: 2655: 2631: 2627: 2625: 2622: 2621: 2604: 2600: 2598: 2595: 2594: 2578: 2575: 2574: 2558: 2555: 2554: 2538: 2535: 2534: 2513: 2512: 2506: 2502: 2481: 2480: 2474: 2470: 2461: 2457: 2444: 2440: 2424: 2422: 2419: 2418: 2403:inference rules 2399: 2370: 2367: 2366: 2344: 2341: 2340: 2324: 2321: 2320: 2303: 2299: 2297: 2294: 2293: 2276: 2272: 2270: 2267: 2266: 2241: 2237: 2228: 2224: 2216: 2213: 2212: 2192: 2189: 2188: 2171: 2167: 2165: 2162: 2161: 2144: 2140: 2138: 2135: 2134: 2115: 2111: 2102: 2098: 2090: 2087: 2086: 2066: 2063: 2062: 2046: 2043: 2042: 2026: 2023: 2022: 1993: 1990: 1989: 1969: 1966: 1965: 1949: 1946: 1945: 1921: 1918: 1917: 1888: 1885: 1884: 1867: 1864: 1863: 1833: 1832: 1817: 1816: 1808: 1803: 1800: 1799: 1772: 1771: 1747: 1746: 1728: 1727: 1703: 1702: 1694: 1691: 1690: 1672: 1669: 1668: 1642: 1641: 1639: 1636: 1635: 1601: 1596: 1593: 1592: 1569: 1568: 1566: 1563: 1562: 1546: 1543: 1542: 1516: 1515: 1513: 1510: 1509: 1493: 1490: 1489: 1466: 1463: 1462: 1445: 1441: 1439: 1436: 1435: 1418: 1414: 1412: 1409: 1408: 1388: 1384: 1382: 1379: 1378: 1358: 1354: 1352: 1349: 1348: 1329: 1326: 1325: 1306: 1303: 1302: 1280: 1277: 1276: 1269: 1238: 1216: 1207: 1202: 1199: 1198: 1172: 1163: 1158: 1155: 1154: 1131: 1126: 1123: 1122: 1106: 1103: 1102: 1083: 1081: 1078: 1077: 1058: 1056: 1053: 1052: 1024: 1022: 1019: 1018: 1002: 999: 998: 987:constant symbol 975: 944: 943: 926: 924: 921: 920: 900: 897: 896: 877: 874: 873: 865:that result in 855: 843:Gregory Bateson 840: 838:Social sciences 743: 740: 739: 707: 704: 703: 687: 684: 683: 667: 664: 663: 658:is the type of 631: 628: 627: 626:A complex type 592: 589: 588: 572: 569: 568: 552: 549: 548: 524: 521: 520: 504: 501: 500: 466: 431: 333: 331:Proof assistant 327: 307:category theory 284: 275: 269: 266: 259:needs expansion 244: 216:Thierry Coquand 181:lambda calculus 108: 102: 90:Thierry Coquand 24: 17: 12: 11: 5: 15191: 15181: 15180: 15175: 15170: 15153: 15152: 15150: 15149: 15144: 15139: 15134: 15129: 15124: 15122:Inferentialism 15119: 15117:Formal grammar 15114: 15109: 15104: 15098: 15096: 15092: 15091: 15088: 15087: 15085: 15084: 15079: 15074: 15069: 15064: 15059: 15054: 15049: 15044: 15039: 15037:Possible world 15034: 15029: 15024: 15019: 15014: 15009: 15004: 14999: 14994: 14989: 14983: 14981: 14977: 14976: 14974: 14973: 14968: 14963: 14958: 14953: 14948: 14943: 14938: 14933: 14928: 14923: 14921:Glue semantics 14918: 14913: 14908: 14903: 14898: 14893: 14887: 14885: 14884:Formal systems 14878: 14874: 14873: 14870: 14869: 14867: 14866: 14861: 14856: 14851: 14846: 14841: 14836: 14831: 14826: 14821: 14816: 14811: 14809:Polarity items 14806: 14801: 14796: 14791: 14786: 14781: 14776: 14771: 14766: 14761: 14756: 14751: 14746: 14741: 14736: 14731: 14726: 14721: 14716: 14711: 14706: 14701: 14696: 14694:Conservativity 14691: 14686: 14681: 14675: 14673: 14669: 14668: 14666: 14665: 14660: 14658:Quantification 14655: 14650: 14645: 14640: 14635: 14630: 14625: 14620: 14615: 14610: 14605: 14600: 14595: 14590: 14584: 14582: 14575: 14571: 14570: 14568: 14567: 14562: 14557: 14552: 14547: 14542: 14537: 14535:Presupposition 14532: 14527: 14522: 14517: 14512: 14507: 14502: 14496: 14494: 14490: 14489: 14482: 14481: 14474: 14467: 14459: 14450: 14449: 14435: 14432: 14431: 14429: 14428: 14423: 14418: 14413: 14408: 14407: 14406: 14396: 14391: 14386: 14377: 14372: 14367: 14362: 14360:Abstract logic 14356: 14354: 14350: 14349: 14347: 14346: 14341: 14339:Turing machine 14336: 14331: 14326: 14321: 14316: 14311: 14310: 14309: 14304: 14299: 14294: 14289: 14279: 14277:Computable set 14274: 14269: 14264: 14259: 14253: 14251: 14245: 14244: 14242: 14241: 14236: 14231: 14226: 14221: 14216: 14211: 14206: 14205: 14204: 14199: 14194: 14184: 14179: 14174: 14172:Satisfiability 14169: 14164: 14159: 14158: 14157: 14147: 14146: 14145: 14135: 14134: 14133: 14128: 14123: 14118: 14113: 14103: 14102: 14101: 14096: 14089:Interpretation 14085: 14083: 14077: 14076: 14074: 14073: 14068: 14063: 14058: 14053: 14043: 14038: 14037: 14036: 14035: 14034: 14024: 14019: 14009: 14004: 13999: 13994: 13989: 13984: 13978: 13976: 13970: 13969: 13966: 13965: 13963: 13962: 13954: 13953: 13952: 13951: 13946: 13945: 13944: 13939: 13934: 13914: 13913: 13912: 13910:minimal axioms 13907: 13896: 13895: 13894: 13883: 13882: 13881: 13876: 13871: 13866: 13861: 13856: 13843: 13841: 13822: 13821: 13819: 13818: 13817: 13816: 13804: 13799: 13798: 13797: 13792: 13787: 13782: 13772: 13767: 13762: 13757: 13756: 13755: 13750: 13740: 13739: 13738: 13733: 13728: 13723: 13713: 13708: 13707: 13706: 13701: 13696: 13686: 13685: 13684: 13679: 13674: 13669: 13664: 13659: 13649: 13644: 13639: 13634: 13633: 13632: 13627: 13622: 13617: 13607: 13602: 13600:Formation rule 13597: 13592: 13591: 13590: 13585: 13575: 13574: 13573: 13563: 13558: 13553: 13548: 13542: 13536: 13519:Formal systems 13515: 13514: 13511: 13510: 13508: 13507: 13502: 13497: 13492: 13487: 13482: 13477: 13472: 13467: 13462: 13461: 13460: 13455: 13444: 13442: 13438: 13437: 13435: 13434: 13433: 13432: 13422: 13417: 13416: 13415: 13408:Large cardinal 13405: 13400: 13395: 13390: 13385: 13371: 13370: 13369: 13364: 13359: 13344: 13342: 13332: 13331: 13329: 13328: 13327: 13326: 13321: 13316: 13306: 13301: 13296: 13291: 13286: 13281: 13276: 13271: 13266: 13261: 13256: 13251: 13245: 13243: 13236: 13235: 13233: 13232: 13231: 13230: 13225: 13220: 13215: 13210: 13205: 13197: 13196: 13195: 13190: 13180: 13175: 13173:Extensionality 13170: 13168:Ordinal number 13165: 13155: 13150: 13149: 13148: 13137: 13131: 13125: 13124: 13121: 13120: 13118: 13117: 13112: 13107: 13102: 13097: 13092: 13087: 13086: 13085: 13075: 13074: 13073: 13060: 13058: 13052: 13051: 13049: 13048: 13047: 13046: 13041: 13036: 13026: 13021: 13016: 13011: 13006: 13001: 12995: 12993: 12987: 12986: 12984: 12983: 12978: 12973: 12968: 12963: 12958: 12953: 12952: 12951: 12941: 12936: 12931: 12926: 12921: 12916: 12910: 12908: 12899: 12893: 12892: 12890: 12889: 12884: 12879: 12874: 12869: 12864: 12852:Cantor's  12850: 12845: 12840: 12830: 12828: 12815: 12814: 12812: 12811: 12806: 12801: 12796: 12791: 12786: 12781: 12776: 12771: 12766: 12761: 12756: 12751: 12750: 12749: 12738: 12736: 12732: 12731: 12724: 12723: 12716: 12709: 12701: 12692: 12691: 12689: 12688: 12678: 12668: 12657: 12654: 12653: 12651: 12650: 12645: 12640: 12635: 12630: 12625: 12620: 12615: 12610: 12605: 12600: 12595: 12590: 12585: 12580: 12575: 12570: 12565: 12560: 12555: 12549: 12547: 12543: 12542: 12540: 12539: 12537:Solid modeling 12534: 12529: 12524: 12519: 12514: 12509: 12504: 12498: 12496: 12490: 12489: 12487: 12486: 12481: 12476: 12471: 12466: 12460: 12458: 12452: 12451: 12449: 12448: 12443: 12438: 12436:Control method 12433: 12428: 12423: 12418: 12413: 12407: 12405: 12399: 12398: 12396: 12395: 12390: 12388:Multithreading 12385: 12380: 12375: 12369: 12367: 12361: 12360: 12358: 12357: 12352: 12347: 12342: 12337: 12331: 12329: 12323: 12322: 12320: 12319: 12314: 12309: 12304: 12299: 12294: 12289: 12284: 12282:Formal methods 12279: 12273: 12271: 12265: 12264: 12262: 12261: 12256: 12254:World Wide Web 12251: 12246: 12241: 12236: 12231: 12226: 12221: 12216: 12211: 12206: 12201: 12196: 12190: 12188: 12182: 12181: 12179: 12178: 12173: 12168: 12163: 12158: 12153: 12148: 12143: 12137: 12135: 12128: 12127: 12125: 12124: 12119: 12114: 12109: 12104: 12098: 12096: 12090: 12089: 12087: 12086: 12081: 12076: 12071: 12066: 12061: 12056: 12055: 12054: 12043: 12041: 12035: 12034: 12032: 12031: 12026: 12021: 12016: 12011: 12006: 12001: 11996: 11991: 11986: 11980: 11978: 11972: 11971: 11969: 11968: 11963: 11958: 11953: 11948: 11943: 11938: 11933: 11928: 11923: 11917: 11915: 11905: 11904: 11902: 11901: 11896: 11891: 11886: 11881: 11875: 11873: 11869: 11868: 11866: 11865: 11860: 11855: 11850: 11845: 11840: 11834: 11832: 11826: 11825: 11823: 11822: 11817: 11812: 11807: 11802: 11796: 11794: 11790: 11789: 11787: 11786: 11777: 11772: 11767: 11762: 11757: 11752: 11747: 11742: 11737: 11731: 11729: 11723: 11722: 11715: 11712: 11711: 11704: 11703: 11696: 11689: 11681: 11675: 11674: 11669: 11668: 11667: 11662: 11647: 11646: 11645: 11632: 11629:The Nuprl Book 11626: 11620: 11603: 11600: 11599: 11598: 11592: 11586: 11580: 11574: 11568: 11562: 11554: 11551: 11549: 11548:External links 11546: 11544: 11543: 11514: 11484: 11451: 11430:(2): 125–154. 11408: 11396: 11363: 11351: 11285: 11259: 11219: 11198: 11173: 11166: 11140: 11110: 11072: 11065: 11030: 11001:Smith, Peter. 10993: 10969: 10950:(3): 407–420. 10927: 10910: 10883: 10864: 10844: 10826: 10806: 10788: 10768: 10750: 10738: 10701:Church, Alonzo 10685: 10663: 10644: 10630: 10628: 10625: 10622: 10621: 10604: 10591: 10574: 10561: 10560: 10558: 10555: 10553: 10552: 10539: 10526: 10500: 10494: 10481: 10475: 10462: 10445: 10429: 10412: 10397: 10379: 10356: 10333: 10325: 10304: 10287: 10275:"Type Systems" 10270: 10248: 10233: 10227: 10214: 10204: 10202: 10199: 10198: 10197: 10192: 10187: 10180: 10177: 10176: 10175: 10169: 10161: 10158: 10157: 10156: 10150: 10139: 10135:some forms of 10133: 10130: 10128:ST type theory 10125: 10118: 10115: 10114: 10113: 10107: 10101: 10096: 10091: 10080: 10077: 10075: 10072: 10055: 10054: 10047: 10040: 10010: 10007: 9992: 9988: 9982: 9978: 9974: 9971: 9966: 9963: 9960: 9956: 9933: 9929: 9925: 9920: 9916: 9912: 9907: 9904: 9901: 9897: 9874: 9869: 9864: 9859: 9854: 9832: 9829: 9826: 9823: 9818: 9796: 9793: 9790: 9787: 9782: 9757: 9754: 9738: 9737: 9734: 9731:Peano's axioms 9715: 9711: 9699: 9679: 9663: 9652: 9637:expressibility 9608: 9605: 9582:Scott encoding 9568: 9565: 9545: 9542: 9539: 9519: 9514: 9511: 9508: 9505: 9484: 9463: 9460: 9457: 9454: 9433: 9430: 9427: 9424: 9421: 9418: 9415: 9395: 9392: 9389: 9369: 9366: 9363: 9343: 9316: 9313: 9298: 9295: 9292: 9288: 9284: 9279: 9276: 9272: 9262: 9259: 9255: 9252: 9249: 9246: 9243: 9240: 9237: 9232: 9229: 9226: 9223: 9218: 9215: 9211: 9207: 9204: 9183: 9180: 9168: 9167: 9155: 9135: 9131: 9126: 9123: 9120: 9117: 9114: 9108: 9105: 9094: 9082: 9062: 9058: 9053: 9050: 9047: 9044: 9038: 9035: 9011: 9008: 9005: 9002: 8999: 8996: 8991: 8988: 8985: 8982: 8977: 8973: 8970: 8947: 8944: 8941: 8938: 8925: 8924: 8912: 8892: 8888: 8883: 8880: 8877: 8874: 8871: 8865: 8862: 8851: 8839: 8819: 8815: 8810: 8807: 8804: 8801: 8795: 8792: 8767: 8764: 8736: 8730: 8727: 8724: 8721: 8699: 8679: 8673: 8670: 8667: 8664: 8642: 8622: 8619: 8613: 8610: 8607: 8604: 8599: 8596: 8593: 8590: 8584: 8581: 8578: 8575: 8570: 8567: 8563: 8560: 8557: 8553: 8550: 8547: 8544: 8541: 8538: 8517: 8497: 8491: 8488: 8485: 8482: 8459: 8456: 8453: 8450: 8447: 8444: 8420: 8400: 8360: 8357: 8345: 8344: 8332: 8328: 8308: 8305: 8300: 8297: 8294: 8291: 8288: 8284: 8280: 8276: 8271: 8268: 8265: 8262: 8259: 8248: 8236: 8232: 8212: 8209: 8204: 8201: 8198: 8195: 8191: 8187: 8183: 8178: 8175: 8172: 8169: 8166: 8142: 8139: 8136: 8133: 8130: 8127: 8124: 8121: 8118: 8115: 8112: 8109: 8106: 8103: 8100: 8097: 8094: 8091: 8088: 8085: 8082: 8079: 8075: 8072: 8069: 8065: 8062: 8059: 8056: 8053: 8028: 8025: 8022: 8019: 8016: 8013: 8010: 8007: 8003: 8000: 7997: 7994: 7991: 7970: 7967: 7964: 7961: 7958: 7955: 7952: 7949: 7945: 7942: 7939: 7936: 7912: 7909: 7906: 7882: 7862: 7850: 7847: 7835: 7834: 7822: 7802: 7799: 7796: 7793: 7790: 7785: 7782: 7779: 7776: 7773: 7770: 7759: 7747: 7727: 7724: 7721: 7718: 7715: 7710: 7707: 7704: 7701: 7698: 7674: 7671: 7668: 7665: 7662: 7659: 7656: 7653: 7649: 7645: 7642: 7639: 7635: 7632: 7629: 7626: 7623: 7620: 7599: 7596: 7593: 7590: 7587: 7584: 7581: 7578: 7574: 7570: 7567: 7564: 7560: 7557: 7554: 7551: 7548: 7527: 7507: 7487: 7467: 7447: 7444: 7441: 7421: 7418: 7415: 7412: 7409: 7389: 7369: 7366: 7363: 7360: 7357: 7342: 7339: 7331:Henk Barendegt 7297: 7294: 7291: 7269: 7249: 7243: 7240: 7237: 7234: 7231: 7228: 7199: 7179: 7176: 7173: 7151: 7148: 7145: 7142: 7120: 7096: 7090: 7087: 7084: 7081: 7067: 7064: 7049: 7046: 7043: 7038: 7033: 7030: 7027: 7022: 7018: 6992: 6989: 6986: 6981: 6978: 6962: 6959: 6945: 6942: 6939: 6936: 6933: 6911: 6908: 6905: 6902: 6880: 6858: 6821: 6818: 6801: 6781: 6778: 6775: 6755: 6735: 6714: 6693: 6677: 6674: 6657: 6637: 6634: 6631: 6611: 6586: 6565: 6549: 6546: 6544: 6541: 6528: 6519:-equality and 6508: 6482: 6478: 6473: 6470: 6467: 6463: 6460: 6456: 6453: 6449: 6444: 6441: 6438: 6434: 6431: 6428: 6425: 6403: 6380: 6360: 6340: 6320: 6300: 6297: 6293: 6290: 6287: 6284: 6281: 6261: 6241: 6221: 6201: 6181: 6178: 6175: 6172: 6169: 6166: 6155: 6154: 6142: 6122: 6098: 6078: 6075: 6072: 6069: 6065: 6062: 6059: 6056: 6053: 6043: 6031: 6011: 6008: 6005: 6002: 5999: 5996: 5993: 5990: 5987: 5983: 5980: 5977: 5974: 5971: 5968: 5945: 5925: 5913: 5910: 5890: 5887: 5884: 5880: 5875: 5872: 5869: 5865: 5861: 5856: 5853: 5850: 5830: 5829: 5811: 5808: 5805: 5802: 5798: 5795: 5790: 5787: 5784: 5780: 5777: 5774: 5771: 5766: 5763: 5760: 5756: 5753: 5743: 5725: 5722: 5719: 5715: 5712: 5707: 5704: 5701: 5697: 5694: 5684: 5666: 5656: 5653: 5650: 5645: 5642: 5639: 5635: 5601: 5598: 5571: 5568: 5541: 5538: 5518: 5498: 5495: 5491: 5488: 5468: 5448: 5428: 5408: 5388: 5385: 5382: 5362: 5342: 5339: 5337: 5334: 5308: 5305: 5302: 5297: 5292: 5289: 5286: 5262: 5259: 5256: 5234: 5230: 5225: 5222: 5219: 5196: 5193: 5190: 5168: 5144: 5141: 5138: 5133: 5128: 5125: 5122: 5117: 5114: 5111: 5107: 5102: 5099: 5096: 5092: 5089: 5086: 5083: 5061: 5041: 5021: 5001: 4981: 4978: 4975: 4955: 4935: 4915: 4912: 4909: 4906: 4903: 4900: 4884: 4881: 4867: 4864: 4861: 4834: 4831: 4828: 4823: 4820: 4815: 4812: 4809: 4804: 4799: 4796: 4793: 4788: 4767: 4764: 4761: 4738: 4735: 4732: 4727: 4722: 4719: 4716: 4693: 4690: 4687: 4664: 4659: 4656: 4653: 4648: 4643: 4640: 4637: 4632: 4629: 4624: 4621: 4618: 4613: 4609: 4606: 4603: 4579: 4576: 4573: 4542: 4522: 4498: 4495: 4492: 4472: 4452: 4432: 4431:Function terms 4429: 4428: 4427: 4414: 4411: 4408: 4405: 4400: 4397: 4387: 4374: 4371: 4368: 4363: 4360: 4350: 4337: 4334: 4331: 4328: 4323: 4319: 4316: 4313: 4310: 4299: 4286: 4283: 4280: 4275: 4272: 4243: 4240: 4237: 4234: 4211: 4208: 4205: 4202: 4199: 4177: 4174: 4171: 4168: 4141: 4138: 4135: 4117: 4114: 4112: 4109: 4107: 4104: 4084: 4081: 4073: 4072: 4071:(Seely, 1984). 4067:correspond to 4062: 4052: 4033:John Lane Bell 4025:Main article: 4022: 4019: 4017: 4016:Research areas 4014: 4008:Type inference 4006:Main article: 4003: 4002:Type inference 4000: 3988:implementation 3971: 3955: 3952: 3923: 3903: 3883: 3863: 3836: 3816: 3796: 3793: 3790: 3787: 3778:with property 3767: 3751: 3748: 3731: 3728: 3725: 3722: 3719: 3716: 3713: 3710: 3707: 3704: 3701: 3698: 3695: 3692: 3672: 3669: 3666: 3663: 3660: 3657: 3654: 3651: 3648: 3645: 3632: 3631: 3630:Dependent Sum 3628: 3617: 3614: 3611: 3608: 3605: 3602: 3599: 3596: 3593: 3583: 3572: 3569: 3566: 3563: 3560: 3557: 3554: 3551: 3548: 3538: 3532: 3531: 3528: 3517: 3514: 3511: 3508: 3505: 3502: 3499: 3496: 3493: 3483: 3472: 3469: 3466: 3463: 3460: 3457: 3454: 3451: 3448: 3438: 3432: 3431: 3428: 3417: 3414: 3411: 3401: 3390: 3387: 3384: 3374: 3368: 3367: 3364: 3353: 3350: 3347: 3337: 3326: 3323: 3320: 3310: 3304: 3303: 3300: 3289: 3286: 3283: 3273: 3262: 3259: 3249: 3243: 3242: 3239: 3228: 3225: 3222: 3212: 3201: 3198: 3195: 3185: 3179: 3178: 3175: 3164: 3154: 3143: 3133: 3129: 3128: 3125: 3114: 3104: 3093: 3083: 3079: 3078: 3075: 3072: 3071:Logic Notation 3069: 3032: 3029: 3013:intuitionistic 3008: 3005: 2997: 2996: 2993: 2990: 2987: 2980: 2979: 2976: 2973: 2970: 2967: 2952: 2949: 2944: 2937: 2916: 2915: 2903: 2883: 2863: 2843: 2823: 2799: 2796: 2793: 2790: 2787: 2784: 2781: 2778: 2775: 2756:Main article: 2753: 2750: 2733: 2730: 2727: 2724: 2721: 2718: 2715: 2714: 2691: 2688: 2685: 2663: 2634: 2630: 2607: 2603: 2582: 2562: 2542: 2509: 2505: 2501: 2498: 2495: 2492: 2489: 2486: 2483: 2482: 2477: 2473: 2469: 2464: 2460: 2456: 2453: 2447: 2443: 2439: 2436: 2433: 2430: 2427: 2426: 2398: 2395: 2374: 2361: 2360: 2348: 2328: 2306: 2302: 2279: 2275: 2263: 2252: 2249: 2244: 2240: 2236: 2231: 2227: 2223: 2220: 2209: 2208: 2196: 2174: 2170: 2147: 2143: 2131: 2118: 2114: 2110: 2105: 2101: 2097: 2094: 2083: 2082: 2070: 2050: 2030: 2020: 2009: 2006: 2003: 2000: 1997: 1986: 1985: 1973: 1953: 1943: 1931: 1928: 1925: 1914: 1913: 1910: 1892: 1871: 1842: 1839: 1836: 1831: 1826: 1823: 1820: 1815: 1811: 1807: 1781: 1778: 1775: 1770: 1767: 1764: 1760: 1756: 1745: 1742: 1737: 1734: 1731: 1726: 1723: 1720: 1715: 1712: 1709: 1706: 1701: 1698: 1676: 1651: 1648: 1645: 1623: 1620: 1616: 1612: 1607: 1604: 1600: 1578: 1575: 1572: 1550: 1528: 1525: 1522: 1519: 1497: 1486: 1485: 1470: 1448: 1444: 1421: 1417: 1405: 1391: 1387: 1361: 1357: 1345: 1333: 1310: 1299: 1284: 1268: 1265: 1252: 1249: 1246: 1241: 1237: 1233: 1228: 1225: 1222: 1219: 1213: 1210: 1206: 1186: 1183: 1180: 1175: 1171: 1166: 1162: 1142: 1139: 1134: 1130: 1110: 1089: 1086: 1061: 1036: 1033: 1030: 1027: 1006: 974: 971: 956: 953: 950: 947: 942: 938: 935: 932: 929: 904: 881: 854: 851: 839: 836: 826:, principally 771: 768: 765: 762: 759: 756: 753: 750: 747: 723: 720: 717: 714: 711: 691: 671: 647: 644: 641: 638: 635: 624: 623: 620: 608: 605: 602: 599: 596: 576: 556: 528: 508: 465: 462: 430: 427: 407: 406: 399: 381: 374: 359: 339:, interactive 337:proof checkers 329:Main article: 326: 323: 317:(specifically 283: 280: 277: 276: 256: 254: 243: 240: 204:Per Martin-Löf 104:Main article: 101: 98: 78: 77: 75:Per Martin-Löf 68: 42:of a specific 15: 9: 6: 4: 3: 2: 15190: 15179: 15176: 15174: 15171: 15169: 15166: 15165: 15163: 15148: 15145: 15143: 15140: 15138: 15135: 15133: 15130: 15128: 15125: 15123: 15120: 15118: 15115: 15113: 15110: 15108: 15105: 15103: 15100: 15099: 15097: 15093: 15083: 15080: 15078: 15075: 15073: 15070: 15068: 15065: 15063: 15060: 15058: 15055: 15053: 15050: 15048: 15045: 15043: 15040: 15038: 15035: 15033: 15030: 15028: 15025: 15023: 15020: 15018: 15015: 15013: 15010: 15008: 15005: 15003: 15000: 14998: 14995: 14993: 14990: 14988: 14985: 14984: 14982: 14978: 14972: 14969: 14967: 14964: 14962: 14959: 14957: 14954: 14952: 14949: 14947: 14944: 14942: 14939: 14937: 14934: 14932: 14929: 14927: 14924: 14922: 14919: 14917: 14914: 14912: 14909: 14907: 14904: 14902: 14899: 14897: 14894: 14892: 14889: 14888: 14886: 14882: 14879: 14875: 14865: 14862: 14860: 14857: 14855: 14852: 14850: 14847: 14845: 14842: 14840: 14837: 14835: 14832: 14830: 14827: 14825: 14822: 14820: 14817: 14815: 14812: 14810: 14807: 14805: 14804:Performatives 14802: 14800: 14797: 14795: 14792: 14790: 14787: 14785: 14784:Logophoricity 14782: 14780: 14777: 14775: 14772: 14770: 14767: 14765: 14762: 14760: 14757: 14755: 14752: 14750: 14747: 14745: 14742: 14740: 14737: 14735: 14732: 14730: 14727: 14725: 14722: 14720: 14717: 14715: 14712: 14710: 14707: 14705: 14702: 14700: 14697: 14695: 14692: 14690: 14687: 14685: 14682: 14680: 14677: 14676: 14674: 14670: 14664: 14661: 14659: 14656: 14654: 14651: 14649: 14646: 14644: 14641: 14639: 14636: 14634: 14631: 14629: 14626: 14624: 14621: 14619: 14618:Evidentiality 14616: 14614: 14611: 14609: 14606: 14604: 14601: 14599: 14596: 14594: 14591: 14589: 14586: 14585: 14583: 14579: 14576: 14572: 14566: 14563: 14561: 14558: 14556: 14553: 14551: 14548: 14546: 14543: 14541: 14538: 14536: 14533: 14531: 14528: 14526: 14523: 14521: 14518: 14516: 14513: 14511: 14508: 14506: 14503: 14501: 14498: 14497: 14495: 14491: 14487: 14480: 14475: 14473: 14468: 14466: 14461: 14460: 14457: 14447: 14446: 14441: 14433: 14427: 14424: 14422: 14419: 14417: 14414: 14412: 14409: 14405: 14402: 14401: 14400: 14397: 14395: 14392: 14390: 14387: 14385: 14381: 14378: 14376: 14373: 14371: 14368: 14366: 14363: 14361: 14358: 14357: 14355: 14351: 14345: 14342: 14340: 14337: 14335: 14334:Recursive set 14332: 14330: 14327: 14325: 14322: 14320: 14317: 14315: 14312: 14308: 14305: 14303: 14300: 14298: 14295: 14293: 14290: 14288: 14285: 14284: 14283: 14280: 14278: 14275: 14273: 14270: 14268: 14265: 14263: 14260: 14258: 14255: 14254: 14252: 14250: 14246: 14240: 14237: 14235: 14232: 14230: 14227: 14225: 14222: 14220: 14217: 14215: 14212: 14210: 14207: 14203: 14200: 14198: 14195: 14193: 14190: 14189: 14188: 14185: 14183: 14180: 14178: 14175: 14173: 14170: 14168: 14165: 14163: 14160: 14156: 14153: 14152: 14151: 14148: 14144: 14143:of arithmetic 14141: 14140: 14139: 14136: 14132: 14129: 14127: 14124: 14122: 14119: 14117: 14114: 14112: 14109: 14108: 14107: 14104: 14100: 14097: 14095: 14092: 14091: 14090: 14087: 14086: 14084: 14082: 14078: 14072: 14069: 14067: 14064: 14062: 14059: 14057: 14054: 14051: 14050:from ZFC 14047: 14044: 14042: 14039: 14033: 14030: 14029: 14028: 14025: 14023: 14020: 14018: 14015: 14014: 14013: 14010: 14008: 14005: 14003: 14000: 13998: 13995: 13993: 13990: 13988: 13985: 13983: 13980: 13979: 13977: 13975: 13971: 13961: 13960: 13956: 13955: 13950: 13949:non-Euclidean 13947: 13943: 13940: 13938: 13935: 13933: 13932: 13928: 13927: 13925: 13922: 13921: 13919: 13915: 13911: 13908: 13906: 13903: 13902: 13901: 13897: 13893: 13890: 13889: 13888: 13884: 13880: 13877: 13875: 13872: 13870: 13867: 13865: 13862: 13860: 13857: 13855: 13852: 13851: 13849: 13845: 13844: 13842: 13837: 13831: 13826:Example  13823: 13815: 13810: 13809: 13808: 13805: 13803: 13800: 13796: 13793: 13791: 13788: 13786: 13783: 13781: 13778: 13777: 13776: 13773: 13771: 13768: 13766: 13763: 13761: 13758: 13754: 13751: 13749: 13746: 13745: 13744: 13741: 13737: 13734: 13732: 13729: 13727: 13724: 13722: 13719: 13718: 13717: 13714: 13712: 13709: 13705: 13702: 13700: 13697: 13695: 13692: 13691: 13690: 13687: 13683: 13680: 13678: 13675: 13673: 13670: 13668: 13665: 13663: 13660: 13658: 13655: 13654: 13653: 13650: 13648: 13645: 13643: 13640: 13638: 13635: 13631: 13628: 13626: 13623: 13621: 13618: 13616: 13613: 13612: 13611: 13608: 13606: 13603: 13601: 13598: 13596: 13593: 13589: 13586: 13584: 13583:by definition 13581: 13580: 13579: 13576: 13572: 13569: 13568: 13567: 13564: 13562: 13559: 13557: 13554: 13552: 13549: 13547: 13544: 13543: 13540: 13537: 13535: 13531: 13526: 13520: 13516: 13506: 13503: 13501: 13498: 13496: 13493: 13491: 13488: 13486: 13483: 13481: 13478: 13476: 13473: 13471: 13470:Kripke–Platek 13468: 13466: 13463: 13459: 13456: 13454: 13451: 13450: 13449: 13446: 13445: 13443: 13439: 13431: 13428: 13427: 13426: 13423: 13421: 13418: 13414: 13411: 13410: 13409: 13406: 13404: 13401: 13399: 13396: 13394: 13391: 13389: 13386: 13383: 13379: 13375: 13372: 13368: 13365: 13363: 13360: 13358: 13355: 13354: 13353: 13349: 13346: 13345: 13343: 13341: 13337: 13333: 13325: 13322: 13320: 13317: 13315: 13314:constructible 13312: 13311: 13310: 13307: 13305: 13302: 13300: 13297: 13295: 13292: 13290: 13287: 13285: 13282: 13280: 13277: 13275: 13272: 13270: 13267: 13265: 13262: 13260: 13257: 13255: 13252: 13250: 13247: 13246: 13244: 13242: 13237: 13229: 13226: 13224: 13221: 13219: 13216: 13214: 13211: 13209: 13206: 13204: 13201: 13200: 13198: 13194: 13191: 13189: 13186: 13185: 13184: 13181: 13179: 13176: 13174: 13171: 13169: 13166: 13164: 13160: 13156: 13154: 13151: 13147: 13144: 13143: 13142: 13139: 13138: 13135: 13132: 13130: 13126: 13116: 13113: 13111: 13108: 13106: 13103: 13101: 13098: 13096: 13093: 13091: 13088: 13084: 13081: 13080: 13079: 13076: 13072: 13067: 13066: 13065: 13062: 13061: 13059: 13057: 13053: 13045: 13042: 13040: 13037: 13035: 13032: 13031: 13030: 13027: 13025: 13022: 13020: 13017: 13015: 13012: 13010: 13007: 13005: 13002: 13000: 12997: 12996: 12994: 12992: 12991:Propositional 12988: 12982: 12979: 12977: 12974: 12972: 12969: 12967: 12964: 12962: 12959: 12957: 12954: 12950: 12947: 12946: 12945: 12942: 12940: 12937: 12935: 12932: 12930: 12927: 12925: 12922: 12920: 12919:Logical truth 12917: 12915: 12912: 12911: 12909: 12907: 12903: 12900: 12898: 12894: 12888: 12885: 12883: 12880: 12878: 12875: 12873: 12870: 12868: 12865: 12863: 12859: 12855: 12851: 12849: 12846: 12844: 12841: 12839: 12835: 12832: 12831: 12829: 12827: 12821: 12816: 12810: 12807: 12805: 12802: 12800: 12797: 12795: 12792: 12790: 12787: 12785: 12782: 12780: 12777: 12775: 12772: 12770: 12767: 12765: 12762: 12760: 12757: 12755: 12752: 12748: 12745: 12744: 12743: 12740: 12739: 12737: 12733: 12729: 12722: 12717: 12715: 12710: 12708: 12703: 12702: 12699: 12687: 12679: 12677: 12669: 12667: 12659: 12658: 12655: 12649: 12646: 12644: 12641: 12639: 12636: 12634: 12631: 12629: 12626: 12624: 12621: 12619: 12616: 12614: 12611: 12609: 12606: 12604: 12601: 12599: 12596: 12594: 12591: 12589: 12586: 12584: 12581: 12579: 12576: 12574: 12571: 12569: 12566: 12564: 12561: 12559: 12556: 12554: 12551: 12550: 12548: 12544: 12538: 12535: 12533: 12530: 12528: 12525: 12523: 12522:Mixed reality 12520: 12518: 12515: 12513: 12510: 12508: 12505: 12503: 12500: 12499: 12497: 12495: 12491: 12485: 12482: 12480: 12477: 12475: 12472: 12470: 12467: 12465: 12462: 12461: 12459: 12457: 12453: 12447: 12444: 12442: 12439: 12437: 12434: 12432: 12429: 12427: 12424: 12422: 12419: 12417: 12414: 12412: 12409: 12408: 12406: 12404: 12400: 12394: 12391: 12389: 12386: 12384: 12381: 12379: 12376: 12374: 12371: 12370: 12368: 12366: 12362: 12356: 12355:Accessibility 12353: 12351: 12350:Visualization 12348: 12346: 12343: 12341: 12338: 12336: 12333: 12332: 12330: 12328: 12324: 12318: 12315: 12313: 12310: 12308: 12305: 12303: 12300: 12298: 12295: 12293: 12290: 12288: 12285: 12283: 12280: 12278: 12275: 12274: 12272: 12270: 12266: 12260: 12257: 12255: 12252: 12250: 12247: 12245: 12242: 12240: 12237: 12235: 12232: 12230: 12227: 12225: 12222: 12220: 12217: 12215: 12212: 12210: 12207: 12205: 12202: 12200: 12197: 12195: 12192: 12191: 12189: 12187: 12183: 12177: 12174: 12172: 12169: 12167: 12164: 12162: 12159: 12157: 12154: 12152: 12149: 12147: 12144: 12142: 12139: 12138: 12136: 12134: 12129: 12123: 12120: 12118: 12115: 12113: 12110: 12108: 12105: 12103: 12100: 12099: 12097: 12095: 12091: 12085: 12082: 12080: 12077: 12075: 12072: 12070: 12067: 12065: 12062: 12060: 12057: 12053: 12050: 12049: 12048: 12045: 12044: 12042: 12040: 12036: 12030: 12027: 12025: 12022: 12020: 12017: 12015: 12012: 12010: 12007: 12005: 12002: 12000: 11997: 11995: 11992: 11990: 11987: 11985: 11982: 11981: 11979: 11977: 11973: 11967: 11964: 11962: 11959: 11957: 11954: 11952: 11949: 11947: 11944: 11942: 11939: 11937: 11934: 11932: 11929: 11927: 11924: 11922: 11919: 11918: 11916: 11914: 11910: 11906: 11900: 11897: 11895: 11892: 11890: 11887: 11885: 11882: 11880: 11877: 11876: 11874: 11870: 11864: 11861: 11859: 11856: 11854: 11851: 11849: 11846: 11844: 11841: 11839: 11836: 11835: 11833: 11831: 11827: 11821: 11818: 11816: 11813: 11811: 11810:Dependability 11808: 11806: 11803: 11801: 11798: 11797: 11795: 11791: 11785: 11781: 11778: 11776: 11773: 11771: 11768: 11766: 11763: 11761: 11758: 11756: 11753: 11751: 11748: 11746: 11743: 11741: 11738: 11736: 11733: 11732: 11730: 11728: 11724: 11719: 11713: 11709: 11702: 11697: 11695: 11690: 11688: 11683: 11682: 11679: 11673: 11670: 11666: 11663: 11661: 11657: 11654: 11653: 11651: 11648: 11643: 11639: 11638: 11636: 11633: 11630: 11627: 11624: 11621: 11617: 11616: 11611: 11606: 11605: 11596: 11593: 11590: 11587: 11584: 11581: 11578: 11575: 11572: 11569: 11566: 11563: 11560: 11557: 11556: 11532: 11528: 11524: 11518: 11502: 11498: 11494: 11488: 11473: 11469: 11465: 11458: 11456: 11446: 11441: 11437: 11433: 11429: 11425: 11424: 11419: 11412: 11399: 11393: 11389: 11385: 11381: 11377: 11370: 11368: 11361: 11358:Balbaert,Ivo 11355: 11347: 11341: 11330: 11325: 11320: 11315: 11310: 11306: 11299: 11292: 11290: 11274: 11270: 11266: 11262: 11256: 11252: 11248: 11243: 11238: 11234: 11230: 11223: 11205: 11201: 11195: 11191: 11184: 11177: 11169: 11163: 11159: 11155: 11151: 11144: 11128: 11124: 11120: 11114: 11096: 11089: 11083: 11081: 11079: 11077: 11068: 11062: 11058: 11057: 11049: 11047: 11045: 11043: 11041: 11039: 11037: 11035: 11015: 11011: 11004: 10997: 10989: 10988: 10980: 10978: 10976: 10974: 10965: 10961: 10957: 10953: 10949: 10945: 10941: 10934: 10932: 10924: 10920: 10914: 10906: 10902: 10899:(2): 99–112. 10898: 10894: 10887: 10880: 10877: 10874: 10868: 10861: 10857: 10854: 10848: 10833: 10829: 10823: 10819: 10818: 10810: 10795: 10791: 10785: 10781: 10780: 10772: 10766: 10764: 10759: 10754: 10748: 10742: 10734: 10730: 10726: 10722: 10718: 10714: 10710: 10706: 10702: 10696: 10694: 10692: 10690: 10682: 10678: 10675: 10672: 10667: 10661: 10657: 10654: 10648: 10641: 10635: 10631: 10614: 10608: 10601: 10595: 10588: 10584: 10578: 10572: 10566: 10562: 10551: 10548: 10544: 10540: 10533: 10529: 10527:90-386-0531-5 10523: 10519: 10515: 10508: 10507: 10501: 10497: 10491: 10487: 10482: 10478: 10476:1-4020-2334-0 10472: 10468: 10463: 10461: 10457: 10454: 10448: 10442: 10438: 10434: 10430: 10419: 10415: 10413:0-201-41667-0 10409: 10405: 10404: 10398: 10394: 10393: 10388: 10387:"Type Theory" 10384: 10380: 10378: 10377: 10372: 10363: 10359: 10357:9789401004138 10353: 10349: 10342: 10338: 10334: 10332:Mathematica'. 10328: 10322: 10318: 10314: 10310: 10305: 10294: 10290: 10288:9780849329098 10284: 10280: 10276: 10271: 10268: 10255: 10251: 10245: 10241: 10240: 10234: 10230: 10224: 10220: 10215: 10211: 10206: 10205: 10196: 10193: 10191: 10188: 10186: 10183: 10182: 10173: 10170: 10167: 10164: 10163: 10155: 10151: 10148: 10144: 10140: 10138: 10134: 10131: 10129: 10126: 10124: 10121: 10120: 10111: 10108: 10105: 10102: 10100: 10097: 10095: 10092: 10090: 10086: 10083: 10082: 10071: 10069: 10064: 10060: 10052: 10048: 10045: 10041: 10038: 10037: 10036: 10033: 10031: 10026: 10022: 10020: 10016: 10006: 9990: 9980: 9976: 9969: 9964: 9961: 9958: 9954: 9931: 9927: 9923: 9918: 9914: 9910: 9905: 9902: 9899: 9895: 9867: 9857: 9830: 9827: 9824: 9821: 9794: 9791: 9788: 9785: 9768: 9766: 9761: 9753: 9751: 9747: 9743: 9735: 9732: 9728: 9724: 9720: 9716: 9712: 9697: 9677: 9669: 9664: 9661: 9657: 9653: 9650: 9646: 9642: 9641: 9640: 9638: 9634: 9630: 9626: 9622: 9618: 9614: 9604: 9602: 9598: 9594: 9590: 9585: 9583: 9579: 9575: 9564: 9562: 9557: 9543: 9540: 9537: 9517: 9482: 9475:. For a term 9431: 9428: 9425: 9422: 9419: 9416: 9413: 9393: 9390: 9387: 9367: 9364: 9361: 9341: 9332: 9330: 9326: 9322: 9321:identity type 9315:Identity type 9312: 9310: 9290: 9286: 9282: 9270: 9260: 9257: 9244: 9238: 9216: 9213: 9209: 9153: 9133: 9129: 9095: 9080: 9060: 9056: 9025: 9024: 9023: 9009: 9003: 8997: 8975: 8910: 8890: 8886: 8852: 8837: 8817: 8813: 8782: 8781: 8780: 8753: 8748: 8734: 8697: 8677: 8640: 8617: 8594: 8588: 8568: 8565: 8555: 8515: 8495: 8432: 8390: 8386: 8382: 8378: 8374: 8370: 8366: 8356: 8354: 8350: 8330: 8326: 8303: 8278: 8274: 8249: 8234: 8230: 8207: 8185: 8181: 8156: 8155: 8154: 8137: 8128: 8125: 8122: 8110: 8104: 8092: 8086: 8080: 8077: 8067: 8042: 8023: 8020: 8017: 8008: 8005: 7965: 7962: 7959: 7950: 7947: 7926: 7910: 7907: 7904: 7896: 7895:tagged unions 7880: 7860: 7846: 7844: 7840: 7820: 7797: 7794: 7791: 7760: 7745: 7722: 7719: 7716: 7688: 7687: 7686: 7669: 7663: 7660: 7657: 7654: 7651: 7647: 7637: 7594: 7588: 7585: 7582: 7579: 7576: 7572: 7562: 7525: 7505: 7485: 7465: 7445: 7442: 7439: 7416: 7413: 7410: 7387: 7364: 7361: 7358: 7348: 7347:ordered pairs 7338: 7336: 7332: 7328: 7323: 7321: 7317: 7313: 7267: 7247: 7215: 7213: 7197: 7177: 7171: 7164:has the type 7118: 7110: 7094: 7063: 7020: 7008: 6979: 6976: 6968: 6958: 6817: 6815: 6799: 6779: 6753: 6733: 6683: 6673: 6671: 6655: 6629: 6609: 6601: 6555: 6540: 6526: 6506: 6498: 6493: 6480: 6476: 6458: 6451: 6447: 6432: 6429: 6426: 6415: 6401: 6392: 6378: 6358: 6338: 6318: 6295: 6291: 6288: 6285: 6282: 6259: 6239: 6219: 6199: 6176: 6173: 6170: 6167: 6140: 6120: 6112: 6111:free variable 6096: 6076: 6067: 6063: 6060: 6057: 6054: 6044: 6029: 6006: 6003: 6000: 5997: 5991: 5985: 5978: 5975: 5972: 5969: 5959: 5958: 5957: 5943: 5923: 5909: 5888: 5882: 5878: 5859: 5839: 5835: 5809: 5800: 5793: 5769: 5744: 5723: 5717: 5710: 5685: 5654: 5648: 5626: 5625: 5624: 5622: 5599: 5596: 5569: 5566: 5539: 5536: 5516: 5493: 5489: 5466: 5446: 5426: 5406: 5386: 5380: 5360: 5352: 5348: 5333: 5331: 5326: 5324: 5232: 5228: 5166: 5157: 5115: 5109: 5105: 5090: 5087: 5084: 5073: 5059: 5039: 5019: 4999: 4979: 4973: 4953: 4933: 4910: 4907: 4904: 4901: 4890: 4880: 4850: 4675: 4611: 4592: 4561: 4559: 4557: 4540: 4520: 4512: 4496: 4490: 4470: 4450: 4442: 4438: 4398: 4395: 4388: 4361: 4358: 4351: 4321: 4300: 4273: 4270: 4263: 4262: 4261: 4259: 4157: 4156:Boolean logic 4123: 4103: 4101: 4097: 4094:differs from 4093: 4089: 4080: 4078: 4070: 4066: 4063: 4061:around 1980); 4060: 4056: 4053: 4050: 4046: 4043: 4042: 4041: 4038: 4034: 4029: 4028: 4013: 4009: 3999: 3997: 3993: 3992:specification 3989: 3984: 3961: 3951: 3949: 3948:parametricity 3945: 3941: 3935: 3921: 3901: 3881: 3861: 3853: 3848: 3834: 3814: 3791: 3785: 3765: 3757: 3747: 3743: 3729: 3705: 3696: 3693: 3661: 3655: 3652: 3649: 3646: 3629: 3612: 3606: 3603: 3600: 3597: 3594: 3584: 3567: 3561: 3558: 3555: 3552: 3549: 3539: 3537: 3534: 3533: 3529: 3512: 3506: 3503: 3500: 3497: 3494: 3484: 3467: 3461: 3458: 3455: 3452: 3449: 3439: 3437: 3434: 3433: 3429: 3415: 3412: 3409: 3402: 3388: 3385: 3382: 3375: 3373: 3370: 3369: 3366:Product Type 3365: 3351: 3348: 3345: 3338: 3324: 3321: 3318: 3311: 3309: 3306: 3305: 3301: 3281: 3274: 3260: 3250: 3248: 3245: 3244: 3240: 3226: 3220: 3213: 3199: 3193: 3186: 3184: 3181: 3180: 3176: 3155: 3134: 3131: 3130: 3126: 3105: 3084: 3081: 3080: 3076: 3074:Type Notation 3073: 3070: 3067: 3066: 3063: 3060: 3058: 3054: 3050: 3046: 3042: 3038: 3028: 3026: 3022: 3018: 3014: 3004: 3002: 2994: 2991: 2988: 2985: 2984: 2983: 2977: 2974: 2971: 2968: 2965: 2961: 2957: 2953: 2950: 2948: 2945: 2942: 2938: 2936:in this case) 2935: 2931: 2930: 2929: 2926: 2924: 2920: 2881: 2861: 2841: 2813: 2812: 2811: 2797: 2794: 2791: 2788: 2785: 2779: 2776: 2765: 2759: 2749: 2731: 2728: 2725: 2722: 2719: 2716: 2661: 2653: 2648: 2632: 2628: 2605: 2601: 2580: 2533: 2532:metavariables 2529: 2507: 2503: 2499: 2496: 2493: 2487: 2475: 2471: 2467: 2462: 2458: 2454: 2445: 2441: 2437: 2434: 2431: 2416: 2412: 2408: 2404: 2394: 2392: 2388: 2372: 2326: 2304: 2300: 2277: 2273: 2264: 2250: 2247: 2242: 2238: 2234: 2229: 2225: 2221: 2211: 2172: 2168: 2145: 2141: 2132: 2116: 2112: 2108: 2103: 2099: 2095: 2085: 2048: 2028: 2021: 2007: 2004: 2001: 1998: 1988: 1951: 1944: 1929: 1926: 1916: 1911: 1908: 1907: 1904: 1882: 1860: 1855: 1813: 1805: 1797: 1794: 1768: 1762: 1758: 1754: 1740: 1724: 1721: 1718: 1699: 1696: 1688: 1674: 1667: 1618: 1614: 1610: 1548: 1495: 1483: 1468: 1461:both of type 1446: 1442: 1419: 1415: 1406: 1389: 1385: 1376: 1359: 1355: 1346: 1331: 1323: 1308: 1300: 1297: 1282: 1274: 1273: 1272: 1264: 1244: 1231: 1178: 1137: 1108: 1076: 1051: 1004: 996: 992: 988: 984: 980: 979:term in logic 970: 940: 918: 902: 895: 879: 872: 868: 864: 860: 850: 848: 844: 835: 833: 829: 825: 821: 817: 816: 811: 807: 803: 801: 797: 793: 789: 785: 766: 763: 757: 754: 751: 737: 718: 715: 712: 689: 669: 661: 642: 639: 636: 621: 603: 600: 597: 574: 554: 546: 545: 544: 542: 526: 506: 497: 495: 491: 487: 483: 479: 476:, especially 475: 471: 461: 459: 455: 450: 448: 444: 440: 436: 426: 424: 420: 416: 412: 404: 400: 397: 393: 389: 385: 382: 379: 375: 372: 368: 364: 360: 357: 353: 350: 349: 348: 346: 342: 338: 332: 322: 320: 316: 312: 308: 303: 301: 297: 293: 289: 273: 264: 260: 257:This section 255: 252: 248: 247: 239: 237: 233: 229: 225: 221: 217: 214:. Another is 213: 209: 205: 200: 198: 194: 190: 186: 182: 178: 177:Alonzo Church 173: 171: 167: 162: 161: 156: 152: 148: 144: 139: 137: 133: 129: 128:Gottlob Frege 125: 121: 117: 113: 107: 97: 95: 91: 87: 83: 76: 72: 69: 67: 66:Alonzo Church 63: 60: 59: 58: 56: 52: 47: 45: 41: 37: 33: 29: 22: 15077:Type shifter 15047:Quantization 14997:Continuation 14965: 14864:Veridicality 14744:Exhaustivity 14709:Cumulativity 14628:Indexicality 14608:Definiteness 14603:Conditionals 14530:Logical form 14436: 14343: 14234:Ultraproduct 14081:Model theory 14046:Independence 13982:Formal proof 13974:Proof theory 13957: 13930: 13887:real numbers 13859:second-order 13770:Substitution 13647:Metalanguage 13588:conservative 13561:Axiom schema 13505:Constructive 13475:Morse–Kelley 13441:Set theories 13420:Aleph number 13413:inaccessible 13319:Grothendieck 13203:intersection 13090:Higher-order 13078:Second-order 13024:Truth tables 12981:Venn diagram 12808: 12764:Formal proof 12618:Cyberwarfare 12277:Cryptography 11615:Scholarpedia 11613: 11535:. Retrieved 11526: 11517: 11505:. Retrieved 11496: 11487: 11476:. Retrieved 11467: 11427: 11421: 11411: 11401:, retrieved 11379: 11354: 11340:cite journal 11304: 11277:. Retrieved 11232: 11222: 11211:. Retrieved 11189: 11176: 11149: 11143: 11131:. Retrieved 11122: 11113: 11102:. Retrieved 11055: 11021:. Retrieved 11009: 10996: 10986: 10947: 10943: 10922: 10918: 10913: 10896: 10892: 10886: 10878: 10875: 10867: 10847: 10836:. Retrieved 10816: 10809: 10798:. Retrieved 10782:. Springer. 10778: 10771: 10762: 10753: 10741: 10711:(2): 56–68. 10708: 10704: 10670: 10666: 10647: 10639: 10634: 10607: 10599: 10594: 10577: 10565: 10550: 10542: 10505: 10485: 10469:. Springer. 10466: 10436: 10422:. Retrieved 10402: 10390: 10374: 10347: 10308: 10297:. Retrieved 10278: 10258:. Retrieved 10238: 10218: 10063:constructive 10056: 10034: 10027: 10023: 10012: 9769: 9762: 9759: 9739: 9610: 9586: 9570: 9558: 9333: 9318: 9311: 9170:The type of 9169: 8926: 8749: 8653:, pass in a 8433: 8362: 8346: 8039:, which are 7925:constructors 7852: 7843:intersection 7836: 7344: 7341:Product type 7324: 7216: 7210:denotes the 7069: 6964: 6823: 6820:Boolean type 6813: 6679: 6669: 6551: 6494: 6416: 6393: 6156: 6153:-reduction). 6042:-reduction). 5915: 5831: 5344: 5327: 5158: 5074: 4886: 4883:Lambda terms 4676: 4593: 4562: 4555: 4434: 4119: 4116:Atomic terms 4086: 4074: 4036: 4030: 4024: 4011: 3991: 3987: 3985: 3957: 3936: 3849: 3753: 3744: 3635: 3061: 3037:propositions 3034: 3010: 3000: 2998: 2981: 2964:transitivity 2940: 2933: 2927: 2917: 2761: 2649: 2415:substitution 2400: 2389:and thus an 2364: 1912:Description 1858: 1856: 1798: 1795: 1689: 1487: 1270: 976: 856: 841: 819: 813: 804: 791: 787: 625: 541:truth-values 498: 493: 489: 467: 451: 432: 408: 334: 304: 295: 285: 267: 263:adding to it 258: 242:Applications 201: 174: 158: 140: 120:formal logic 109: 79: 48: 35: 25: 15168:Type theory 14992:Context set 14966:Type theory 14849:Subtrigging 14613:Disjunction 14540:Proposition 14344:Type theory 14292:undecidable 14224:Truth value 14111:equivalence 13790:non-logical 13403:Enumeration 13393:Isomorphism 13340:cardinality 13324:Von Neumann 13289:Ultrafilter 13254:Uncountable 13188:equivalence 13105:Quantifiers 13095:Fixed-point 13064:First-order 12944:Consistency 12929:Proposition 12906:Traditional 12877:Lindström's 12867:Compactness 12809:Type theory 12754:Cardinality 12628:Video games 12608:Digital art 12365:Concurrency 12234:Data mining 12146:Probability 11879:Interpreter 11133:29 December 11023:29 December 10925:. Elsevier. 10453:Book review 10371:Paul Halmos 10317:11375/12315 10143:lambda cube 10087:which is a 9717:Set theory 9495:, the call 8363:Two common 7897:. The type 7400:. The pair 7335:lambda cube 7320:dot product 7316:type safety 6670:uninhabited 6539:-equality. 5509:, has type 5209:. The term 4106:Definitions 3183:Implication 3177:Empty Type 2956:reflexivity 2923:consistency 2834:and a type 1375:is equal to 871:proposition 847:double bind 818:to express 464:Linguistics 354:is used by 44:type system 36:type theory 28:mathematics 15162:Categories 15142:Pragmatics 14789:Mirativity 14555:Speech act 14510:Entailment 14505:Denotation 14155:elementary 13848:arithmetic 13716:Quantifier 13694:functional 13566:Expression 13284:Transitive 13228:identities 13213:complement 13146:hereditary 13129:Set theory 12686:Glossaries 12558:E-commerce 12151:Statistics 12094:Algorithms 12052:Stochastic 11884:Middleware 11740:Peripheral 11658:including 11537:2022-01-21 11507:21 January 11478:2022-01-22 11445:2066/17240 11403:2024-01-18 11314:1611.02108 11279:2022-06-21 11242:2101.11479 11213:2012-11-03 11104:2022-01-22 10838:2022-07-29 10800:2022-07-29 10627:References 10424:2006-04-03 10373:'s (1960) 10299:2004-06-26 10260:2020-07-19 9591:, such as 9022:such that 8389:set theory 8153:such that 6554:empty type 6548:Empty type 6414:-reduced. 5912:Reductions 4059:Dana Scott 4037:themselves 3944:canonicity 3127:Unit Type 3077:Type Name 3068:Logic Name 2652:proof tree 294:to encode 51:set theory 15178:Hierarchy 14941:Mereology 14877:Formalism 14759:Givenness 14684:Cataphora 14672:Phenomena 14663:Vagueness 14593:Ambiguity 14545:Reference 14525:Intension 14515:Extension 14426:Supertask 14329:Recursion 14287:decidable 14121:saturated 14099:of models 14022:deductive 14017:axiomatic 13937:Hilbert's 13924:Euclidean 13905:canonical 13828:axiomatic 13760:Signature 13689:Predicate 13578:Extension 13500:Ackermann 13425:Operation 13304:Universal 13294:Recursive 13269:Singleton 13264:Inhabited 13249:Countable 13239:Types of 13223:power set 13193:partition 13110:Predicate 13056:Predicate 12971:Syllogism 12961:Soundness 12934:Inference 12924:Tautology 12826:paradoxes 12507:Rendering 12502:Animation 12133:computing 12084:Semantics 11775:Processor 11523:"Axiom K" 11269:231719089 10964:1573-0964 10653:v.1 Types 10435:(2008) . 10385:(2018) . 10339:(2012) . 9970:≅ 9962:× 9924:× 9911:≅ 9868:≅ 9828:≅ 9822:× 9792:≅ 9631:with the 9619:with the 9291:τ 9287:σ 9254:Σ 9248:→ 9245:τ 9242:→ 9239:σ 9236:→ 9214:τ 9210:σ 9206:Π 9154:τ 9134:τ 9130:σ 9081:σ 9061:τ 9057:σ 9007:→ 9001:→ 8995:→ 8976:: 8598:→ 8592:→ 8562:Π 8419:Σ 8399:Π 8138:ρ 8135:→ 8129:τ 8126:⊔ 8123:σ 8117:→ 8111:ρ 8108:→ 8105:τ 8099:→ 8093:ρ 8090:→ 8087:σ 8078:ρ 8074:Π 8041:injective 8024:τ 8021:⊔ 8018:σ 8012:→ 8009:τ 7966:τ 7963:⊔ 7960:σ 7954:→ 7951:σ 7911:τ 7908:⊔ 7905:σ 7881:⊔ 7670:τ 7667:→ 7664:τ 7661:× 7658:σ 7652:τ 7648:σ 7644:Π 7595:σ 7592:→ 7589:τ 7586:× 7583:σ 7577:τ 7573:σ 7569:Π 7506:τ 7466:σ 7446:τ 7443:× 7440:σ 7388:× 7175:→ 7037:→ 6814:inhabited 6777:→ 6774:⊤ 6734:∗ 6692:⊤ 6682:unit type 6676:Unit type 6636:⊥ 6633:→ 6564:⊥ 6527:η 6507:β 6462:→ 6427:λ 6402:β 6283:λ 6168:λ 6141:η 6109:is not a 6074:→ 6055:λ 6030:β 6001:: 5989:→ 5970:λ 5944:η 5924:β 5665:→ 5517:τ 5427:σ 5387:τ 5384:→ 5381:σ 5296:→ 5245:has type 5132:→ 5085:λ 5040:τ 5000:σ 4980:τ 4977:→ 4974:σ 4902:λ 4879:'s type. 4822:→ 4803:→ 4726:→ 4647:→ 4628:→ 4541:τ 4521:σ 4511:parameter 4497:τ 4494:→ 4491:σ 4471:τ 4451:σ 4437:functions 4055:C-monoids 3970:→ 3727:→ 3721:⊥ 3718:→ 3712:⊥ 3709:→ 3691:Π 3668:⊥ 3665:→ 3644:Π 3592:Σ 3553:∈ 3547:∃ 3492:Π 3453:∈ 3447:∀ 3430:Sum Type 3386:∨ 3349:× 3322:∧ 3288:⊥ 3285:→ 3258:¬ 3241:Function 3224:→ 3197:→ 3163:⊥ 3142:⊥ 3113:⊤ 3092:⊤ 2941:weakening 2902:Γ 2882:τ 2842:τ 2822:Γ 2795:τ 2786:⊢ 2783:Γ 2774:∃ 2717:⊢ 2561:Δ 2541:Γ 2528:rewriting 2494:⊢ 2491:Δ 2485:Γ 2455:⊢ 2452:Δ 2432:⊢ 2429:Γ 2411:deduction 2391:extrinsic 2373:≡ 2347:Γ 2222:⊢ 2219:Γ 2195:Γ 2096:⊢ 2093:Γ 2069:Γ 1999:⊢ 1996:Γ 1972:Γ 1927:⊢ 1924:Γ 1891:Δ 1870:Γ 1830:→ 1806:⊢ 1741:⊢ 1675:⊢ 1482:are equal 1322:is a term 1296:is a type 1267:Judgments 903:φ 880:φ 867:judgments 788:everybody 770:⟩ 761:⟩ 749:⟨ 746:⟨ 722:⟩ 710:⟨ 660:functions 646:⟩ 634:⟨ 607:⟩ 595:⟨ 441:phase of 151:Whitehead 15095:See also 14980:Concepts 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10293:Archived 10254:Archived 10179:See also 10123:Automath 10099:system F 9621:language 9146:returns 9073:returns 8903:returns 8830:returns 8381:products 8319:returns 8223:returns 7849:Sum type 7813:returns 7738:returns 7458:, where 7260:, where 7212:universe 7190:, where 6497:equality 5323:argument 4992:, where 4926:, where 4513:of type 4158:values ( 4051:, 1970); 3934:exists. 2960:symmetry 2674:of type 1324:of type 991:variable 796:Montague 443:compiler 415:Isabelle 319:homotopy 288:Automath 270:May 2008 166:subtypes 14598:Binding 14353:Related 14150:Diagram 14048: ( 14027:Hilbert 14012:Systems 14007:Theorem 13885:of the 13830:systems 13610:Formula 13605:Grammar 13521: ( 13465:General 13178:Forcing 13163:Element 13083:Monadic 12858:paradox 12799:Theorem 12735:General 12676:Outline 11468:YouTube 10760:at the 10725:2266170 8690:and an 6792:, then 6648:, then 6391:to it. 5621:deduced 3436:For All 2954:define 2934:context 2810:) is: 2409:-style 2407:Gentzen 1859:context 1407:"Terms 993:, or a 894:formula 815:records 800:Barwise 786:, like 155:Russell 112:paradox 100:History 38:is the 15027:Monads 14574:Topics 14116:finite 13879:Skolem 13832:  13807:Theory 13775:Symbol 13765:String 13748:atomic 13625:ground 13620:closed 13615:atomic 13571:ground 13534:syntax 13430:binary 13357:domain 13274:Finite 13039:finite 12897:Logics 12856:  12804:Theory 11394:  11267:  11257:  11196:  11164:  11063:  10962:  10824:  10786:  10731:  10723:  10524:  10492:  10473:  10443:  10410:  10354:  10323:  10285:  10246:  10225:  10015:axioms 10009:Axioms 9649:axioms 9625:axioms 7312:vector 5589:, and 5399:, and 5032:, and 4556:simple 4256:, and 4049:Lambek 3536:Exists 2620:, and 2530:. 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Index

Form (architecture) § Theories
mathematics
theoretical computer science
formal presentation
type system
set theory
foundation of mathematics
Typed λ-calculus
Alonzo Church
Intuitionistic type theory
Per Martin-Löf
computerized proof-writing systems
their foundation
Thierry Coquand
Calculus of Inductive Constructions
History of type theory
paradox
naive set theory
formal logic
Russell's paradox
Gottlob Frege
The Foundations of Arithmetic
Bertrand Russell
ramified theory of types
axiom of reducibility
Whitehead
Russell
Principia Mathematica
subtypes
Zermelo-Fraenkel set theory

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