Syntactically and semantically regular languages of lambda-terms coincide through logical relations

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Hauptverfasser: Moreau, Vincent, Nguyên, Lê Thành Dũng
Format: Preprint
Veröffentlicht: 2023
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author Moreau, Vincent
Nguyên, Lê Thành Dũng
author_facet Moreau, Vincent
Nguyên, Lê Thành Dũng
contents A fundamental theme in automata theory is regular languages of words and trees, and their many equivalent definitions. Salvati has proposed a generalization to regular languages of simply typed $λ$-terms, defined using denotational semantics in finite sets. We provide here some evidence for its robustness. First, we give an equivalent syntactic characterization that naturally extends the seminal work of Hillebrand and Kanellakis connecting regular languages of words and syntactic $λ$-definability. Second, we show that any finitary extensional model of the simply typed $λ$-calculus, when used in Salvati's definition, recognizes exactly the same class of languages of $λ$-terms as the category of finite sets does. The proofs of these two results rely on logical relations and can be seen as instances of a more general construction of a categorical nature, inspired by previous categorical accounts of logical relations using the gluing construction.
format Preprint
id arxiv_https___arxiv_org_abs_2308_00198
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Syntactically and semantically regular languages of lambda-terms coincide through logical relations
Moreau, Vincent
Nguyên, Lê Thành Dũng
Logic in Computer Science
Formal Languages and Automata Theory
Programming Languages
A fundamental theme in automata theory is regular languages of words and trees, and their many equivalent definitions. Salvati has proposed a generalization to regular languages of simply typed $λ$-terms, defined using denotational semantics in finite sets. We provide here some evidence for its robustness. First, we give an equivalent syntactic characterization that naturally extends the seminal work of Hillebrand and Kanellakis connecting regular languages of words and syntactic $λ$-definability. Second, we show that any finitary extensional model of the simply typed $λ$-calculus, when used in Salvati's definition, recognizes exactly the same class of languages of $λ$-terms as the category of finite sets does. The proofs of these two results rely on logical relations and can be seen as instances of a more general construction of a categorical nature, inspired by previous categorical accounts of logical relations using the gluing construction.
title Syntactically and semantically regular languages of lambda-terms coincide through logical relations
topic Logic in Computer Science
Formal Languages and Automata Theory
Programming Languages
url https://arxiv.org/abs/2308.00198