Bidirectional Interpolation for the Lambda-Calculus -- Revisiting and Formalising Craig-Čubrić Interpolation

Fuente: arXiv
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Main Authors: Bertrand, Meven Lennon, Saurin, Alexis
Format: Preprint
Published: 2026
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author Bertrand, Meven Lennon
Saurin, Alexis
author_facet Bertrand, Meven Lennon
Saurin, Alexis
contents Craig's Interpolation theorem has a wide range of applications, from mathematical logic to computer science. Proof-theoretic techniques for establishing interpolation usually follow a method first introduced by Maehara for the Sequent Calculus and then adapted by Prawitz to Natural Deduction. The result can be strengthened to a proof-relevant version, taking proof terms into account: this was first established by Čubrić in the simply-typed lambda-calculus with sums and more recently in linear, classical and intuitionistic sequent calculi. We give a new proof of Čubrić's proof-relevant interpolation theorem by building on principles of bidirectional typing, and formalise it in Rocq.
format Preprint
id arxiv_https___arxiv_org_abs_2603_03083
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Bidirectional Interpolation for the Lambda-Calculus -- Revisiting and Formalising Craig-Čubrić Interpolation
Bertrand, Meven Lennon
Saurin, Alexis
Logic in Computer Science
Programming Languages
Logic
F.4.1; I.2.3
Craig's Interpolation theorem has a wide range of applications, from mathematical logic to computer science. Proof-theoretic techniques for establishing interpolation usually follow a method first introduced by Maehara for the Sequent Calculus and then adapted by Prawitz to Natural Deduction. The result can be strengthened to a proof-relevant version, taking proof terms into account: this was first established by Čubrić in the simply-typed lambda-calculus with sums and more recently in linear, classical and intuitionistic sequent calculi. We give a new proof of Čubrić's proof-relevant interpolation theorem by building on principles of bidirectional typing, and formalise it in Rocq.
title Bidirectional Interpolation for the Lambda-Calculus -- Revisiting and Formalising Craig-Čubrić Interpolation
topic Logic in Computer Science
Programming Languages
Logic
F.4.1; I.2.3
url https://arxiv.org/abs/2603.03083