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A lambda proof of the P-W theorem

Published online by Cambridge University Press:  12 March 2014

Sachio Hirokawa
Affiliation:
Computer Center, Kyushu University, Hakozaki 6-10-1, Fukuoka 812-8581, Japan, E-mail:hirokawa@cc.kyushu-u.ac.jp
Yuichi Komori
Affiliation:
Department of Mathematics, Faculty of Science, Chiba University, Yayoi-Cho 1-33, Inage-Ku. CHIBA 263-8522, Japan, E-mail:komori@math.s.chiba-u.ac.jp
Misao Nagayama
Affiliation:
Department of Mathematics, Tokyo Woman's Christian University, Zempuku-JI 2-6-1, Suginami, Tokyo 167-8585, Japan, E-mail:misao@twcu.ac.jp

Abstract

The logical system P-W is an implicational non-commutative intuitionistic logic denned by axiom schemes B − (bc) → (ab) → ac. B′ = (ab) → (bc) → ac. I - aa with the rules of modus ponens and substitution. The P-W problem is a problem asking whether α - β holds if α → β and β → α are both provable in P-W. The answer is affirmative. The first to prove this was E. P. Martin by a semantical method.

In this paper, we give the first proof of Martin's theorem based on the theory of simply typed λ-calculus. This proof is obtained as a corollary to the main theorem of this paper, shown without using Martin's Theorem, that any closed hereditary right-maximal linear (HRML) λ-term of type α → α is βη-reducible to λxx. Here the HRML λ-terms correspond, via the Curry-Howard isomorphism, to the P-W proofs in natural deduction style.

Information

Type
Research Article
Copyright
Copyright © Association for Symbolic Logic 2000

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