Simon Helsen, Peter Thiemann
Polymorphic Specialization for ML
We present a novel technique for offline partial evaluation of functional languages with an ML-style typing discipline. Our program specialization method comprises a polymorphic binding-time analysis with polymorphic recursion. Based on the region calculus of Tofte and Talpin, we develop a binding-time analysis as a constraint analysis on top of region inference. Our insight is to regard binding times as properties of regions. Specialization is specified as a small-step semantics, extending previous work on syntactic type soundness results for the region calculus. Using similar syntactic proof techniques, we prove soundness of the binding-time analysis with respect to the specializer. In addition, we prove that specialization preserves the call-by-value semantics of the region calculus by showing that the reductions of the specializer are contextual equivalences in the region calculus.