A Decision Procedure for a Theory of Finite Sets with Finite Integer Intervals

In this paper we extend a decision procedure for the Boolean algebra of finite sets with cardinality constraints (L-vertical bar center dot vertical bar) to a decision procedure for L-vertical bar center dot vertical bar extended with set terms denoting finite integer intervals (L-[]). In L-[] interval limits can be integer linear terms including unbounded variables. These intervals are a useful extension because they allow to express non-trivial set operators such as the minimum and maximum of a set, still in a quantifier-free logic. Hence, by providing a decision procedure for L-[] it is possible to automatically reason about a new class of quantifier-free formulas. The decision procedure is implemented as part of the {log} ('setlog') tool. The paper includes a case study based on the elevator algorithm showing that {log} can automatically discharge all its invariance lemmas, some of which involve intervals.