Compiling a Functional Logic Language: The Fair Scheme

Abstract. We present a compilation scheme for a functional logic programming language. The input program to our compiler is a constructor-based graph rewrit-ing system in a non-confluent, but well-behaved class. This input is an interme-diate representation of a functional logic program in a language such as Curry or T OY. The output program from our compiler consists of three procedures that make recursive calls and execute both rewrite and pull-tab steps. This output is an intermediate representation that is easy to encode in any number of programming languages. Our design evolves the Basic Scheme of Antoy and Peters by removing the “left bias ” that prevents obtaining results of some computations—a behavior related to the order of evaluation, which is counter to declarative programming. The benefits of this evolution are not only the strong completeness of computa-tions, but also the provability of non-trivial properties of these computations. We rigorously describe the compiler design and prove some of its properties. To state and prove these properties, we introduce novel definitions of “need ” and “fail-ure. ” For non-confluent constructor-based rewriting systems these concepts are more appropriate than the classic definition of need of Huet and Levy

A New Functional-Logic Compiler for Curry: SPRITE

We introduce a new native code compiler for Curry codenamed Sprite. Sprite is based on the Fair Scheme, a compilation strategy that provides instructions for transforming declarative, non-deterministic programs of a certain class into imperative, deterministic code. We outline salient features of Sprite, discuss its implementation of Curry programs, and present benchmarking results. Sprite is the first-to-date operationally complete implementation of Curry. Preliminary results show that ensuring this property does not incur a significant penalty