|Kawa - Compiling Dynamic Languages to the Java VM|
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Starting in 1995 Cygnus (on behalf of the Free Software Foundation) developed Guile, an implementation of Scheme suitable as a general embedding and extension language. Guile was based on Aubrey Jaffar's SCM interpreter; the various Guile enhancements were initially done by Tom Lord. In 1995 we got a major contract to enhance Guile, and with our client we added more features, including threads (primarily done by Anthony Green), and internationalization.
The contract called for a byte-code compiler for Guile, and it looked like doing a good job on this would be a major project. One option we considered was compiling Scheme into Java bytecodes and executing them by a Java engine. The disadvantage would be that such a Scheme system would not co-exist with Guile (on the other hand, we had run into various technical and non-technical problems with Guile that led us to conclude that Guile would after all not be strategic to Cygnus). The advantage of a Java solution was leveraging off the tools and development being done in the Java “space”, plus that Java was more likely to be strategic long-term.
The customer agreed to using Java, and I started active development June 1996. As a base, I used the Kawa Scheme interpreter written by R. Alexander Milowski. He needed an object-oriented Scheme interpreter to implement DSSSL DSSSL, a Scheme-like environment for expressing style, formatting, and other processing of SGML SGML documents. DSSSL is an subset of “pure” Scheme with some extensions. Kawa 0.2 was a simple interpreter which was far from complete. It provided a useful starting point, but almost all of the original code has by now been re-written.
Kawa 1.0 was released to our customer and “the Net” September 1996. Development has continued since then, at a less intense pace! The long-term goal is an object-oriented environment that harmoniously integrates Scheme, Java, EcmaScript, and other languages.
|Kawa - Compiling Dynamic Languages to the Java VM||Basic implementation strategy|