Rob Nederpelt | Searcharxiv

arXiv2026

An Unconventional View on Beta-Reduction in Namefree Lambda-Calculus

Terms in the lambda-calculus can be represented as planar trees decorated with symbols for abstraction and application, and having variables as leaves. In this paper, we concentrate on the branches of such trees, rather than on the trees themselves. We reformulate several well-known notions of beta-reduction in this view. In a natural manner, this reconsideration eventually leads to a new form of beta-reduction, being expanding in the sense that the reduction of term t1 to term t2 entails that the tree of t1 is a subtree of the tree of t2.

cs.LO↗

arXiv2022

Characteristics of de Bruijn's early proof checker Automath

The `mathematical language' Automath, conceived by N.G. de Bruijn in 1968, was the first theorem prover actually working and was used for checking many specimina of mathematical content. Its goals and syntactic ideas inspired Th. Coquand and G. Huet to develop the calculus of constructions, CC, which was one of the first widely used interactive theorem provers and forms the basis for the widely used Coq system. The original syntax of Automath is not easy to grasp. Yet, it is essentially based on a derivation system that is similar to the Calculus of Constructions (`CC'). The relation between the Automath syntax and CC has not yet been sufficiently described, although there are many references in the type theory community to Automath. In this paper we focus on the backgrounds and on some uncommon aspects of the syntax of Automath. We expose the fundamental aspects of a `generic' Automath system, encapsulating the most common versions of Automath. We present this generic Automath system in a modern syntactic frame. The obtained system makes use of {\lambda}D, a direct extension of CC with definitions.

cs.LO↗