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Some lambda calculus and type theory formalized
 Journal of Automated Reasoning
, 1999
"... Abstract. We survey a substantial body of knowledge about lambda calculus and Pure Type Systems, formally developed in a constructive type theory using the LEGO proof system. On lambda calculus, we work up to an abstract, simplified, proof of standardization for beta reduction, that does not mention ..."
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Cited by 53 (7 self)
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Abstract. We survey a substantial body of knowledge about lambda calculus and Pure Type Systems, formally developed in a constructive type theory using the LEGO proof system. On lambda calculus, we work up to an abstract, simplified, proof of standardization for beta reduction, that does not mention redex positions or residuals. Then we outline the meta theory of Pure Type Systems, leading to the strengthening lemma. One novelty is our use of named variables for the formalization. Along the way we point out what we feel has been learned about general issues of formalizing mathematics, emphasizing the search for formal definitions that are convenient for formal proof and convincingly represent the intended informal concepts.
A realizability interpretation of MartinLöf's type theory
"... In this paper we present a simple argument for normalization of the fragment of MartinLöf's type theory that contains the natural numbers, dependent function types and the first universe. We do this by building a realizability model of this theory which directly reflects that terms and types are ge ..."
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Cited by 8 (1 self)
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In this paper we present a simple argument for normalization of the fragment of MartinLöf's type theory that contains the natural numbers, dependent function types and the first universe. We do this by building a realizability model of this theory which directly reflects that terms and types are generated simultaneously.
Categories and Subject Descriptors: F.4.1 [Mathematical Logic and Formal Languages]:
"... The formal system λδ is a typed λcalculus that pursues the unification of terms, types, environments and contexts as the main goal. λδ takes some features from the Automathrelated λcalculi and some from the pure type systems, but differs from both in that it does not include the Π construction wh ..."
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The formal system λδ is a typed λcalculus that pursues the unification of terms, types, environments and contexts as the main goal. λδ takes some features from the Automathrelated λcalculi and some from the pure type systems, but differs from both in that it does not include the Π construction while it provides for an abbreviation mechanism at the level of terms. λδ enjoys some important desirable properties such as the confluence of reduction, the correctness of types, the uniqueness of types up to conversion, the subject reduction of the type assignment, the strong normalization of the typed terms and, as a corollary, the decidability of type inference problem.
UITP 2010 Pollackinconsistency
"... For interactive theorem provers a very desirable property is consistency: it should not be possible to prove false theorems. However, this is not enough: it also should not be possible to think that a theorem that actually is false has been proved. More precisely: the user should be able to know wha ..."
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For interactive theorem provers a very desirable property is consistency: it should not be possible to prove false theorems. However, this is not enough: it also should not be possible to think that a theorem that actually is false has been proved. More precisely: the user should be able to know what it is that the interactive theorem prover is proving. To make these issues concrete we introduce the notion of Pollackconsistency. This property is related to a system being able to correctly parse formulas that it printed itself. In current systems it happens regularly that this fails. We argue that a good interactive theorem prover should be Pollackconsistent. We show with examples that many interactive theorem provers currently are not Pollackconsistent. Finally we describe a simple approach for making a system Pollackconsistent, which only consists of a small modification to the printing code of the system. The most intelligent creature in the universe is a rock. None would know it because they have lousy I/O. — quote from the Internet
The Formal System λδ
, 2008
"... The formal system λδ is a typed λcalculus that pursues the unification of terms, types, environments and contexts as the main goal. λδ takes some features from the Automathrelated λcalculi and some from the pure type systems, but differs from both in that it does not include the Π construction wh ..."
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The formal system λδ is a typed λcalculus that pursues the unification of terms, types, environments and contexts as the main goal. λδ takes some features from the Automathrelated λcalculi and some from the pure type systems, but differs from both in that it does not include the Π construction while it provides for an abbreviation mechanism at the level of terms. λδ enjoys some important desirable properties such as the confluence of reduction, the correctness of types, the uniqueness of types up to conversion, the subject reduction of the type assignment, the strong normalization of the typed terms and, as a corollary, the decidability of type inference problem.
The Formal System λδ
, 2008
"... The formal system λδ is a typed λcalculus that pursues the unification of terms, types, environments and contexts as the main goal. λδ takes some features from the Automathrelated λcalculi and some from the pure type systems, but differs from both in that it does not include the Π construction wh ..."
Abstract
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The formal system λδ is a typed λcalculus that pursues the unification of terms, types, environments and contexts as the main goal. λδ takes some features from the Automathrelated λcalculi and some from the pure type systems, but differs from both in that it does not include the Π construction while it provides for an abbreviation mechanism at the level of terms. λδ enjoys some important desirable properties such as the confluence of reduction, the correctness of types, the uniqueness of types up to conversion, the subject reduction of the type assignment, the strong normalization of the typed terms and, as a corollary, the decidability of type inference problem.
λTypes on the λCalculus with Abbreviations
, 2007
"... In this paper the author presents λδ, a λtyped λcalculus with a single λ binder and abbreviations. This calculus pursues the reuse of the term constructions both at the level of types and at the level of contexts as the main goal. Up to conversion λδ shares with Church λ → the subset of typable te ..."
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In this paper the author presents λδ, a λtyped λcalculus with a single λ binder and abbreviations. This calculus pursues the reuse of the term constructions both at the level of types and at the level of contexts as the main goal. Up to conversion λδ shares with Church λ → the subset of typable terms but in the “propositions as types ” perspective it can encode the implicative fragment of predicative logic without quantifiers because dependent types are allowed. λδ enjoys the properties of Church λ → (mainly subject conversion, strong normalization and decidability of type inference) and, in addition, it satisfies the correctness of types and the uniqueness of types up to conversion. We stress that λδ differs from the Automathrelated λcalculi in that they do not provide for an abbreviation construction at the level of terms. Moreover, unlike many λcalculi, λδ features a type hierarchy with an infinite number of levels both above and below any reference point.