Deciding Functional Lists with Sublist Sets

摘要

Motivated by the problem of deciding verification conditions for the verification of functional programs, we present new decision pro cedures for automated reasoning about functional lists. We first show how to decide in NP the satisfiability problem for logical constraints containing equality, constructor, selectors, as well as the transitive sub list relation. We then extend this class of constraints with operators to compute the set of all sublists, and the set of objects stored in a list. Finally, we support constraints on sizes of sets, which gives us the ability to compute list length as well as the number of distinct list elements. We show that the extended theory is reducible to the theory of sets with linear cardinality constraints, and therefore still in NP. This reduc tion enables us to combine our theory with other decidable theories that impose constraints on sets of objects, which further increases the poten tial of our decidability result in verification of functional and imperative software.