Verifying Catamorphism-Based Contracts using Constrained Horn Clauses

We address the problem of verifying that functions a program meet their contracts, specified by pre/postconditions. follow an approach based on constrained Horn clauses (CHCs) which verification is reduced to checking satisfiability set derived from given and contracts. consider programs manipulate algebraic data types (ADTs) class contracts catamorphisms, is, defined simple recursion schemata ADTs. show several examples state-of-the-art CHC tools are not effective at solving problems obtained direct translation into CHCs. To overcome this difficulty, we propose transformation technique removes ADT terms CHCs derives new sets work basic sorts only, such as integers booleans. Thus, when using there no need for induction rules prove sound, if satisfiable, then so original set. also always terminates catamorphisms. Finally, present experimental results implementation our many non-trivial manipulating programs.