226:
Gradual typing allows software developers to choose either type paradigm as appropriate, from within a single language. In many cases gradual typing is added to an existing dynamic language, creating a derived language allowing but not requiring static typing to be used. In some cases a language uses
390:
has gradual typing for object pointers with respect to method calls. Static typing is used when a variable is typed as pointer to a certain class of object: when a method call is made to the variable, the compiler statically checks that the class is declared to support such a method, or it generates
270:
with respect to subtyping. The main idea is that consistency and subtyping are orthogonal ideas that compose nicely. To add subtyping to a gradually-typed language, simply add the subsumption rule and add a subtyping rule that makes the dynamic type a subtype of itself, because subtyping is supposed
258:
is transitive, that results in every type becoming related to every other type, and so subtyping would no longer rule out any static type errors. The addition of a second phase of plausibility checking to the type system did not completely solve this problem.
350:
has been developed, adding coercion, error propagation and filtering to the normal validation properties of the type system as well as applying type functions outside of function definitions, thereby the increasing flexibility of type definitions.
894:
Siek, Jeremy G.; Vitousek, Michael M.; Cimini, Matteo; Boyland, John Tang (2015). Ball, Thomas; Bodik, Rastislav; Krishnamurthi, Shriram; Lerner, Benjamin S.; Morrisett, Greg (eds.).
380:(formerly Perl6) has gradual typing implemented from the start. Type checks occur at all locations where values are assigned or bound. An "untyped" variable or parameter is typed as
384:, which will match (almost) all values. The compiler flags type-checking conflicts at compile time if it can determine at compile time that they will never succeed.
254:
Prior attempts at integrating static and dynamic typing tried to make the dynamic type be both the top and bottom of the subtype hierarchy. However, because
898:. Leibniz International Proceedings in Informatics. Vol. 32. Dagstuhl, Germany: Schloss Dagstuhl–Leibniz-Zentrum fuer Informatik. pp. 274–293.
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started as a statically typed language, but as of version 4.0 is gradually typed, allowing variables to be explicitly marked as dynamic by using the
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that relates the dynamic type to every other type. The consistency relation is reflexive and symmetric but not transitive.
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Proceedings of the 2014 ACM International
Conference on Object Oriented Programming Systems Languages & Applications
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Gradual typing can easily be integrated into the type system of an object-oriented language that already uses the
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is used to represent statically-unknown types. The notion of type equality is replaced by a new relation called
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Proceedings of the 41st ACM SIGPLAN-SIGACT Symposium on
Principles of Programming Languages - POPL '14
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Proceedings of the 17th ACM SIGPLAN-SIGACT symposium on
Principles of programming languages - POPL '90
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Swamy, N.; Fournet, C.; Rastogi, A.; Bhargavan, K.; Chen, J.; Strub, P. Y.; Bierman, G. (2014).
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Examples of gradually typed languages derived from existing dynamically typed languages include
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The term was coined by Jeremy Siek, who developed gradual typing in 2006 with Walid Taha.
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type. Gradually typed languages not derived from a dynamically typed language include
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Proceedings of the
Symposium on Object-Oriented Programming Systems, Companion Volume
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and expressions may be given types and the correctness of the typing is checked at
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to be reflexive. (But do not make the top of the subtyping order dynamic!)
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871:"The JS++ Type System, Appendix B: Problems (Why was this hard to solve?)"
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600:"Checking correctness of TypeScript interfaces for JavaScript libraries"
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Siek, Jeremy; Taha, Walid (August 2007). "Gradual Typing for
Objects".
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is used, the compiler will allow any method to be called on it.
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is a gradually typed language that is now an implementation of
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Aseem
Rastogi; Avik Chaudhuri; Basil Hosmer (January 2012).
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programming language, released in 2011, is a superset of
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211:) and some expressions may be left untyped and eventual
678:"PHP: Function arguments - Manual » Strict typing"
406:(dynamically typed) with a gradual type system that is
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a warning or error. However, if a variable of the type
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Proceedings of the
Principles of Programming Languages
565:. Lecture Notes in Computer Science. Vol. 4609.
693:"Interlanguage Migration: From Scripts to Programs"
608:. Portland, Oregon, USA: ACM Press. pp. 1–16.
458:OOPSLA'04 Workshop on Revival of Dynamic Languages
323:(alternative static type checker for Python), or
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639:"Gradual typing embedded securely in JavaScript"
550:(Technical report). Boston University. 1994-013.
780:"Pyre - A performant type-checker for Python 3"
719:"The Design and Implementation of Typed Scheme"
597:
499:Thatte, Satish (1990). "Quasi-static typing".
295:(for PHP), PHP (since 7.0), Typed Racket (for
547:An Algorithm for Inferring Quasi-Static Types
165:
795:"The Ins and Outs of Gradual Type Inference"
471:Siek, Jeremy; Taha, Walid (September 2006).
436:
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717:Tobin-Hochstadt, Sam; Felleisen, Matthias.
691:Tobin-Hochstadt, Sam; Felleisen, Matthias.
766:"mypy - Optional Static Typing for Python"
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598:Feldthaus, Asger; Møller, Anders (2014).
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563:ECOOP 2007 – Object-Oriented Programming
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243:In gradual typing, a special type named
474:Gradual Typing for Functional Languages
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482:Scheme and Functional Programming 2006
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896:Refined Criteria for Gradual Typing
802:Association for Computing Machinery
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725:. San Diego, CA. Tobin-Hochstadt08
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699:. Portland, OR. Tobin-Hochstadt06
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227:gradual typing from the start.
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437:Siek, Jeremy (24 March 2014).
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905:10.4230/lipics.snapl.2015.274
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575:10.1007/978-3-540-73589-2_2
315:(a static type checker for
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10:
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745:"Typed Clojure User Guide"
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439:"What is gradual typing?"
843:"dynamic (C# Reference)"
544:Oliart, Alberto (1994).
454:"Pluggable Type Systems"
654:10.1145/2535838.2535889
614:10.1145/2660193.2660215
266:rule to allow implicit
452:Bracha, Gilad (2004).
348:J programming language
299:), Typed Clojure (for
42:Strong vs. weak typing
486:University of Chicago
648:. pp. 425–437.
507:. pp. 367–381.
191:that lies inbetween
513:10.1145/96709.96747
418:API corner cases.
764:Jukka Lehtosalo.
623:978-1-4503-2585-1
584:978-3-540-73588-5
569:. pp. 2–27.
488:. pp. 81–92.
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848:MSDN Library
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121:Intersection
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851:. Microsoft
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311:compiler),
264:subsumption
249:consistency
213:type errors
189:type system
85:Duck typing
37:Type safety
16:Type system
855:14 January
808:2014-09-23
729:2020-11-06
703:2020-11-06
422:References
412:ECMAScript
404:JavaScript
337:ECMAScript
289:JavaScript
287:(both for
285:TypeScript
219:(which is
207:(which is
131:Refinement
80:structural
341:HyperTalk
327:(a typed
256:subtyping
201:variables
106:Dependent
935:Category
924:15383644
567:Springer
275:Examples
101:Abstract
71:inferred
67:Manifest
531:8725290
360:dynamic
301:Clojure
268:upcasts
245:dynamic
231:History
217:runtime
199:. Some
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146:Session
116:Gradual
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317:Python
309:Python
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527:S2CID
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