Hybrid contract checking via symbolic simplification
Résumé
Program errors are hard to detect or prove absent. Allowing programmers to write formal and precise specifications, especially in the form of contracts, is a popular approach to program verification and error discovery. We formalize and implement a hybrid (static and dynamic) contract checker for a subset of OCaml. The key technique is symbolic simplification, which makes integrating static and dynamic contract checking easy and effective. Our technique statically checks contract satisfaction or blames the function violating the contract. When a contract satisfaction is undecidable, it leaves residual code for dynamic contract checking.