Higher-Order Model Checking in Direct Style

Abstract

Higher-order model checking, or model checking of higher-order recursion schemes, has been recently applied to fully automated verification of functional programs. The previous approach has been indirect, in the sense that higher-order functional programs are first abstracted to (call-by-value) higher-order Boolean programs, and then further translated to higher-order recursion schemes (which are essentially call-by-name programs) and model checked. These multi-step transformations caused a number of problems such as code explosion. In this paper, we advocate a more direct approach, where higher-order Boolean programs are directly model checked, without transformation to higher-order recursion schemes. To this end, we develop a model checking algorithm for higher-order call-by-value Boolean programs, and prove its correctness. According to experiments, our prototype implementation outperforms the indirect method for large instances.