New Rewriter Features in FGL

TL;DR

FGL introduces new programmable rewrite features that enhance the flexibility and power of the ACL2 proof procedure, enabling more precise and maintainable rewriting rules using syntactic information.

Contribution

The paper presents novel rewrite features in FGL that improve programmability and ease of use compared to traditional ACL2 rewriter, with technical solutions and feasibility analysis.

Findings

New rewrite features enable more powerful rule programming.

Features facilitate using syntactic information in rewrite rules.

Assessment shows potential for integrating features into ACL2 rewriter.

Abstract

FGL is a successor to GL, a proof procedure for ACL2 that allows complicated finitary conjectures to be translated into efficient Boolean function representations and proved using SAT solvers. A primary focus of FGL is to allow greater programmability using rewrite rules. While the FGL rewriter is modeled on ACL2's rewriter, we have added several features in order to make rewrite rules more powerful. A particular focus is to make it more convenient for rewrite rules to use information from the syntactic domain, allowing them to replace built-in primitives and meta rules in many cases. Since it is easier to write, maintain, and prove the soundness of rewrite rules than to do the same for rules programmed at the syntactic level, these features help make it feasible for users to precisely program the behavior or the rewriter. We describe the new features that FGL's rewriter implements, discuss the solutions to some technical problems that we encountered in their implementation, and assess the feasibility of adding these features to the ACL2 rewriter.