Elsevier

Theoretical Computer Science

Volume 103, Issue 2, 14 September 1992, Pages 387-394
Theoretical Computer Science

Note
A simple proof of a theorem of Statman

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Abstract

In this note, we reprove a theorem of Statman that deciding the βη-equality of two first-order typable λ-terms is not elementary recursive (Statman, 1982). The basic idea of our proof, like that of Statman's is the Henkin quantifier elimination procedure (Henkin, 1963). However, our coding is much simpler, and easy to understand.

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On leave from Brandeis University, Waltham, Massachusetts, Supported in part by NSF Grant CCR-9017125, and grants from Texas Instruments and from the Tyson Foundation.