Free Monads, Intrinsic Scoping, and Higher-Order Preunification

Fuente: arXiv
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Auteur principal: Kudasov, Nikolai
Format: Preprint
Publié: 2022
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author Kudasov, Nikolai
author_facet Kudasov, Nikolai
contents Type checking algorithms and theorem provers rely on unification algorithms. In presence of type families or higher-order logic, higher-order (pre)unification (HOU) is required. Many HOU algorithms are expressed in terms of $λ$-calculus and require encodings, such as higher-order abstract syntax, which are sometimes not comfortable to work with for language implementors. To facilitate implementations of languages, proof assistants, and theorem provers, we propose a novel approach based on the second-order abstract syntax of Fiore, data types à la carte of Swierstra, and intrinsic scoping of Bird and Patterson. With our approach, an object language is generated freely from a given bifunctor. Then, given an evaluation function and making a few reasonable assumptions on it, we derive a higher-order preunification procedure on terms in the object language. More precisely, we apply a variant of $E$-unification for second-order syntax. Finally, we briefly demonstrate an application of this technique to implement type checking (with type inference) for Martin-Löf Type Theory, a dependent type theory.
format Preprint
id arxiv_https___arxiv_org_abs_2204_05653
institution arXiv
publishDate 2022
record_format arxiv
spellingShingle Free Monads, Intrinsic Scoping, and Higher-Order Preunification
Kudasov, Nikolai
Logic in Computer Science
Type checking algorithms and theorem provers rely on unification algorithms. In presence of type families or higher-order logic, higher-order (pre)unification (HOU) is required. Many HOU algorithms are expressed in terms of $λ$-calculus and require encodings, such as higher-order abstract syntax, which are sometimes not comfortable to work with for language implementors. To facilitate implementations of languages, proof assistants, and theorem provers, we propose a novel approach based on the second-order abstract syntax of Fiore, data types à la carte of Swierstra, and intrinsic scoping of Bird and Patterson. With our approach, an object language is generated freely from a given bifunctor. Then, given an evaluation function and making a few reasonable assumptions on it, we derive a higher-order preunification procedure on terms in the object language. More precisely, we apply a variant of $E$-unification for second-order syntax. Finally, we briefly demonstrate an application of this technique to implement type checking (with type inference) for Martin-Löf Type Theory, a dependent type theory.
title Free Monads, Intrinsic Scoping, and Higher-Order Preunification
topic Logic in Computer Science
url https://arxiv.org/abs/2204.05653