First-Class Data-Type Representations in SchemeXerox

Abstract

In most programming language implementations, the compiler has detailed knowledge of the representations of and operations on primitive data typed and data-type constructors. In SCHEMEXEROX, this knowledge is almost entirely external to the compiler, in ordinary, procedural user code. The primitive representations and operations are embodied in first-class “representation types” that are constructed and implemented in an abstract and high-level fashion. Despite this abstractness, a few generally-useful optimizing transformations are sufficient to allow the SCHEMEXEROX compiler to generate efficient code for the primitive operations, essentially as good as could be achieved using more contorted, traditional techniques.