Scala to the Power of Z3: Integrating SMT and Programming

We describe a system that integrates the SMT solver Z3 with the Scala programming language. The system supports the use of the SMT solver for checking satisfiability, unsatisfiability, as well as solution enumeration. The embedding of formula trees into Scala uses the host type system of Scala to prevent the construction of certain ill-typed constraints. The solution enumeration feature integrates into the iteration constructions of Scala and supports writing non-deterministic programs. Using Z3's mechanism of theory extensions, our system also helps users construct custom constraint solvers where the interpretation of predicates and functions is given as Scala code. The resulting system preserves the productivity advantages of Scala while simplifying tasks such as combinatorial search.