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Domain theoretic models of polymorphism
 Inf. Comput
, 1989
"... We give an illustration of a construction useful in producing and describing models of Girard and Reynolds' polymorphic λcalculus. The key unifying ideas are that of a Grothendieck fibration and the category of continuous sections associated with it, constructions used in indexed category theo ..."
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Cited by 34 (2 self)
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We give an illustration of a construction useful in producing and describing models of Girard and Reynolds' polymorphic λcalculus. The key unifying ideas are that of a Grothendieck fibration and the category of continuous sections associated with it, constructions used in indexed category theory; the universal types of the calculus are interpreted as the category of continuous sections of the fibration. As a major example a new model for the polymorphic λcalculus is presented. In it a type is interpreted as a Scott domain. In fact, understanding universal types of the polymorphic λcalculus as categories of continuous sections appears to be useful generally. For example, the technique also applies to the finitary projection model of Bruce and Longo, and a recent model of Girard. (Indeed the work here was inspired by Girard's and arose through trying to extend the construction of his model to Scott domains.) It is hoped that by pinpointing a key construction this paper will help towards a deeper understanding of models for the polymorphic λcalculus and the
Constructions, Inductive Types and Strong Normalization
, 1993
"... This thesis contains an investigation of Coquand's Calculus of Constructions, a basic impredicative Type Theory. We review syntactic properties of the calculus, in particular decidability of equality and typechecking, based on the equalityasjudgement presentation. We present a settheoretic ..."
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Cited by 33 (2 self)
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This thesis contains an investigation of Coquand's Calculus of Constructions, a basic impredicative Type Theory. We review syntactic properties of the calculus, in particular decidability of equality and typechecking, based on the equalityasjudgement presentation. We present a settheoretic notion of model, CCstructures, and use this to give a new strong normalization proof based on a modification of the realizability interpretation. An extension of the core calculus by inductive types is investigated and we show, using the example of infinite trees, how the realizability semantics and the strong normalization argument can be extended to nonalgebraic inductive types. We emphasize that our interpretation is sound for large eliminations, e.g. allows the definition of sets by recursion. Finally we apply the extended calculus to a nontrivial problem: the formalization of the strong normalization argument for Girard's System F. This formal proof has been developed and checked using the...
Total Functional Programming
 Journal of Universal Computer Science
, 2004
"... We now define the notion, already discussed, of an effectively calculable function of positive integers by identifying it with the notion of a recursive function of positive integers (or of a lambdadefinable function of positive integers). The phrase in parentheses refers to the apparatus which Chur ..."
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Cited by 31 (1 self)
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We now define the notion, already discussed, of an effectively calculable function of positive integers by identifying it with the notion of a recursive function of positive integers (or of a lambdadefinable function of positive integers). The phrase in parentheses refers to the apparatus which Church had developed to investigate this and other problems in the foundations of mathematics: the calculus of lambda conversion. Both the Thesis and the lambda calculus have been of seminal influence on the development of Computing Science. The main subject of this article is the lambda calculus but I will begin with a brief sketch of the emergence of the Thesis. The epistemological status of Church’s Thesis is not immediately clear from the above quotation and remains a matter of debate, as is explored in other papers of this volume. My own view, which I will state but not elaborate here, is that the thesis is empirical because it relies for its significance on a claim about what can be calculated by mechanisms. This becomes clearer in
Inductionrecursion and initial algebras
 Annals of Pure and Applied Logic
, 2003
"... 1 Introduction Inductionrecursion is a powerful definition method in intuitionistic type theory in the sense of Scott ("Constructive Validity") [31] and MartinL"of [17, 18, 19]. The first occurrence of formal inductionrecursion is MartinL"of's definition ..."
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Cited by 29 (11 self)
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1 Introduction Inductionrecursion is a powerful definition method in intuitionistic type theory in the sense of Scott (&quot;Constructive Validity&quot;) [31] and MartinL&quot;of [17, 18, 19]. The first occurrence of formal inductionrecursion is MartinL&quot;of's definition of a universe `a la Tarski [19], which consists of a set U
Propositions as [Types]
, 2001
"... Image factorizations in regular categories are stable under pullbacks, so they model a natural modal operator in dependent type theory. This unary type constructor [A] has turned up previously in a syntactic form as a way of erasing computational content, and formalizing a notion of proof irrelevanc ..."
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Cited by 28 (0 self)
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Image factorizations in regular categories are stable under pullbacks, so they model a natural modal operator in dependent type theory. This unary type constructor [A] has turned up previously in a syntactic form as a way of erasing computational content, and formalizing a notion of proof irrelevance. Indeed, semantically, the notion of a support is sometimes used as surrogate proposition asserting inhabitation of an indexed family. We give rules for bracket types in dependent type theory and provide complete semantics using regular categories. We show that dependent type theory with the unit type, strong extensional equality types, strong dependent sums, and bracket types is the internal type theory of regular categories, in the same way that the usual dependent type theory with dependent sums and products is the internal type theory of locally cartesian closed categories. We also show how to interpret rstorder logic in type theory with brackets, and we make use of the translation to compare type theory with logic. Specically, we show that the propositionsastypes interpretation is complete with respect to a certain fragment of intuitionistic rstorder logic. As a consequence, a modied doublenegation translation into type theory (without bracket types) is complete for all of classical rstorder logic.
Implicit Syntax
 Informal Proceedings of First Workshop on Logical Frameworks
, 1992
"... A proof checking system may support syntax that is more convenient for users than its `official' language. For example LEGO (a typechecker for several systems related to the Calculus of Constructions) has algorithms to infer some polymorphic instantiations (e.g. pair 2 true instead of pair n ..."
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Cited by 22 (2 self)
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A proof checking system may support syntax that is more convenient for users than its `official' language. For example LEGO (a typechecker for several systems related to the Calculus of Constructions) has algorithms to infer some polymorphic instantiations (e.g. pair 2 true instead of pair nat bool 2 true) and universe levels (e.g. Type instead of Type(4)). Users need to understand such features, but do not want to know the algorithms for computing them. In this note I explain these two features by nondeterministic operational semantics for "translating" implicit syntax to the fully explicit underlying formal system. The translations are sound and complete for the underlying type theory, and the algorithms (which I will not talk about) are sound (not necessarily complete) for the translations. This note is phrased in terms of a general class of type theories. The technique described has more general application. 1 Introduction Consider the usual formal system, !, for simp...
Constrained Types for ObjectOriented Languages
"... Abstract. X10 is a modern objectoriented language designed for productivity and performance in concurrent and distributed systems. In this setting, dependent types offer significant opportunities for detecting design errors statically, documenting design decisions, eliminating costly runtime checks ..."
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Cited by 15 (1 self)
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Abstract. X10 is a modern objectoriented language designed for productivity and performance in concurrent and distributed systems. In this setting, dependent types offer significant opportunities for detecting design errors statically, documenting design decisions, eliminating costly runtime checks (e.g., for array bounds, null values), and improving the quality of generated code. We present the design and implementation of constrained types, a natural, simple, clean, and expressive extension to objectoriented programming: A type C(:c) names a class or interface C and a constraint c on the immutable state of C and inscope final variables. Constraints may also be associated with class definitions (representing class invariants) and with method and constructor definitions (representing preconditions). Dynamic casting is permitted. The system is parametric on the underlying constraint system: the compiler supports a simple equalitybased constraint system but, in addition, supports extension with new constraint systems using compiler plugins. 1