Chez Scheme

Since 1985

Chez Scheme is one of the "big three" early implementations which to this day serve as the gold standard for a full-featured Scheme system. Like its contemporary MIT Scheme, and in contrast to Gambit, it is an implementation in the "Lisp system" style and the entire environment must be deployed as a unit.

Many consider Chez Scheme a flagship implementation due to its dependability, advanced optimizer, completeness of features and documentation, and strict standards conformance. However, language implementation is a complex pursuit and there are any number of niches where others come out ahead.

Chez Scheme is based around an incremental native-code compiler similar to that of the Common Lisp implementation SBCL. Code typed into the REPL is compiled the same way as code loaded from a source file. The compiler can do some optimization across module boundaries, even as code is loaded incrementally. Compilation is fast enough that REPL use is instantaneous.

There is a separate bytecode interpreter called Petite Chez Scheme which supports the same language as the main implementation but is more portable. Chez Scheme used to be a closed source commercial product, Petite being a demo available at no cost. Both are now open source. Chez Scheme serves as the engine behind recent versions of Racket.

Visit the Chez Scheme home page