Faster Smarter Induction in Isabelle/HOL with SeLFiE

Proof by induction is a long-standing challenge in Computer Science. Induction tactics of proof assistants facilitate proof by induction, but rely on humans to manually specify how to apply induction. In this paper, we present SeLFiE, a domain-specific language to encode experienced users' expertise on how to apply the induct tactic in Isabelle/HOL: when we apply an induction heuristic written in SeLFiE to an inductive problem and arguments to the induct tactic, the SeLFiE interpreter examines both the syntactic structure of the problem and semantics of the relevant constants to judge whether the arguments to the induct tactic are plausible according to the heuristic. Then, we present semantic_induct, an automatic tool to recommend how to apply the induct tactic. Given an inductive problem, semantic_induct produces candidate arguments to the induct tactic and selects promising ones using heuristics written in SeLFiE. Our evaluation based on 254 inductive problems from nine problem domains show that semantic_induct achieved 15.7 percentage points of improvements in coincidence rates for the three most promising recommendations while achieving 43% of reduction in the median value for the execution time when compared to an existing tool, smart_induct.