Formal Correctness of a Quadratic Unification Algorithm

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) Issue Title: Empirically Successful Automated Reasoning: Applications Issue We present a case study using ACL2 to verify a nontrivial algorithm that uses efficient data structures. The algorithm receives as input two first-order terms, and it returns a most general unifier of these terms if they are unifiable, failure otherwise. The verified implementation stores terms as directed acyclic graphs by means of a pointer structure. Its time complexity is ... and its space complexity ..., and it can be executed in ACL2 at a speed comparable to a similar C implementation. We report the main issues encountered to achieve this formally verified implementation.[PUBLICATION ABSTRACT]