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A General Formulation of Simultaneous InductiveRecursive Definitions in Type Theory
 Journal of Symbolic Logic
, 1998
"... The first example of a simultaneous inductiverecursive definition in intuitionistic type theory is MartinLöf's universe à la Tarski. A set U0 of codes for small sets is generated inductively at the same time as a function T0 , which maps a code to the corresponding small set, is defined by recursi ..."
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Cited by 65 (9 self)
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The first example of a simultaneous inductiverecursive definition in intuitionistic type theory is MartinLöf's universe à la Tarski. A set U0 of codes for small sets is generated inductively at the same time as a function T0 , which maps a code to the corresponding small set, is defined by recursion on the way the elements of U0 are generated. In this paper we argue that there is an underlying general notion of simultaneous inductiverecursive definition which is implicit in MartinLöf's intuitionistic type theory. We extend previously given schematic formulations of inductive definitions in type theory to encompass a general notion of simultaneous inductionrecursion. This enables us to give a unified treatment of several interesting constructions including various universe constructions by Palmgren, Griffor, Rathjen, and Setzer and a constructive version of Aczel's Frege structures. Consistency of a restricted version of the extension is shown by constructing a realisability model ...
Program extraction from normalization proofs
 Typed Lambda Calculi and Applications, number 664 in Lecture Notes in Computer Science
, 1993
"... This paper describes formalizations of Tait’s normalization proof for the simply typed λcalculus in the proof assistants Minlog, Coq and Isabelle/HOL. From the formal proofs programs are machineextracted that implement variants of the wellknown normalizationbyevaluation algorithm. The case stud ..."
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Cited by 60 (5 self)
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This paper describes formalizations of Tait’s normalization proof for the simply typed λcalculus in the proof assistants Minlog, Coq and Isabelle/HOL. From the formal proofs programs are machineextracted that implement variants of the wellknown normalizationbyevaluation algorithm. The case study is used to test and compare the program extraction machineries of the three proof assistants in a nontrivial setting. 1
Internal Type Theory
 Lecture Notes in Computer Science
, 1996
"... . We introduce categories with families as a new notion of model for a basic framework of dependent types. This notion is close to ordinary syntax and yet has a clean categorical description. We also present categories with families as a generalized algebraic theory. Then we define categories with f ..."
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Cited by 36 (7 self)
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. We introduce categories with families as a new notion of model for a basic framework of dependent types. This notion is close to ordinary syntax and yet has a clean categorical description. We also present categories with families as a generalized algebraic theory. Then we define categories with families formally in MartinLof's intensional intuitionistic type theory. Finally, we discuss the coherence problem for these internal categories with families. 1 Introduction In a previous paper [8] I introduced a general notion of simultaneous inductiverecursive definition in intuitionistic type theory. This notion subsumes various reflection principles and seems to pave the way for a natural development of what could be called "internal type theory", that is, the construction of models of (fragments of) type theory in type theory, and more generally, the formalization of the metatheory of type theory in type theory. The present paper is a first investigation of such an internal type theor...
From semantics to rules: A machine assisted analysis
 Proceedings of CSL '93, LNCS 832
, 1999
"... this paper is similar to the one in [2]. In this paper they define a normalization function for simply typed ..."
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Cited by 29 (0 self)
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this paper is similar to the one in [2]. In this paper they define a normalization function for simply typed
A Semantic Account of TypeDirected Partial Evaluation
 In Gopalan Nadathur, editor, International Conference on Principles and Practice of Declarative Programming, number 1702 in Lecture
, 1999
"... We formally characterize partial evaluation of functional programs as a normalization problem in an equational theory, and derive a typebased normalizationbyevaluation algorithm for computing normal forms in this setting. We then establish the correctness of this algorithm using a semantic ar ..."
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Cited by 25 (2 self)
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We formally characterize partial evaluation of functional programs as a normalization problem in an equational theory, and derive a typebased normalizationbyevaluation algorithm for computing normal forms in this setting. We then establish the correctness of this algorithm using a semantic argument based on Kripke logical relations. For simplicity, the results are stated for a nonstrict, purely functional language; but the methods are directly applicable to stating and proving correctness of typedirected partial evaluation in MLlike languages as well.
Categorical Reconstruction of a Reduction Free Normalization Proof
, 1995
"... Introduction We present a categorical proof of the normalization theorem for simply typed calculus, i.e. we derive a computable function nf which assigns to every typed term a normal form, s.t. M ' N nf(M ) = nf(N ) nf(M ) ' M where ' is fij equality. Both the function nf and its correctness ..."
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Cited by 22 (5 self)
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Introduction We present a categorical proof of the normalization theorem for simply typed calculus, i.e. we derive a computable function nf which assigns to every typed term a normal form, s.t. M ' N nf(M ) = nf(N ) nf(M ) ' M where ' is fij equality. Both the function nf and its correctness properties can be deduced from the categorical construction. To substantiate this, we present an ML program in the appendix which can be extracted from our argument. We emphasize that this presentation of normalization is reduction free, i.e. we do not mention term rewriting or use properties of term rewriting systems such as the ChurchRosser property. An immediate consequence of normalization is the decidability of ' but there are other useful corollaries; for instance we can show that
From ReductionBased to ReductionFree Normalization
, 2004
"... We present a systematic construction of a reductionfree normalization function. Starting from ..."
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Cited by 21 (8 self)
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We present a systematic construction of a reductionfree normalization function. Starting from
Normalization and partial evaluation
 Applied Semantics, number 2395 in LNCS
, 2002
"... Abstract. We give an introduction to normalization by evaluation and typedirected partial evaluation. We first present normalization by evaluation for a combinatory version of Gödel System T. Then we show normalization by evaluation for typed lambda calculus with β and η conversion. Finally, we int ..."
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Cited by 17 (0 self)
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Abstract. We give an introduction to normalization by evaluation and typedirected partial evaluation. We first present normalization by evaluation for a combinatory version of Gödel System T. Then we show normalization by evaluation for typed lambda calculus with β and η conversion. Finally, we introduce the notion of binding time, and explain the method of typedirected partial evaluation for a small PCFstyle functional programming language. We give algorithms for both callbyname and callbyvalue versions of this language.
Extracting a Proof of Coherence for Monoidal Categories from a Proof of Normalization for Monoids
 In TYPES
, 1995
"... . This paper studies the problem of coherence in category theory from a typetheoretic viewpoint. We first show how a CurryHoward interpretation of a formal proof of normalization for monoids almost directly yields a coherence proof for monoidal categories. Then we formalize this coherence proof in ..."
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Cited by 16 (3 self)
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. This paper studies the problem of coherence in category theory from a typetheoretic viewpoint. We first show how a CurryHoward interpretation of a formal proof of normalization for monoids almost directly yields a coherence proof for monoidal categories. Then we formalize this coherence proof in intensional intuitionistic type theory and show how it relies on explicit reasoning about proof objects for intensional equality. This formalization has been checked in the proof assistant ALF. 1 Introduction Mac Lane [18, pp.161165] proved a coherence theorem for monoidal categories. A basic ingredient in his proof is the normalization of object expressions. But it is only one ingredient and several others are needed too. Here we show that almost a whole proof of this coherence theorem is hidden in a CurryHoward interpretation of a proof of normalization for monoids. The second point of the paper is to contribute to the development of constructive category theory in the sense of Huet a...