A Transformation Based on the Equality between Terms

Abstract

We present a new transformation of Prolog programs preserving operational equivalence. Our transformation — EBC (equality based continuation) transformation — relies on the introduction of equations between terms. These equations are used to introduce alternative and more efficient representations of terms. When applied to binary Prolog programs, EBC is able to perform the following optimizations by mere source to source transformations: removal of existential variables in programs using difference lists and accumulators, reduction of the number of occur-checks, interprocedural register allocation when executed on the WAM, linearization of recursions, optimization of continuation-like user data structures.