The scheme of things

I decided to begin my tenure on this column by describing two recent proposals for additions to Scheme. The first is a facility for creating new, programmer-defined da ta types; the second makes it possible for procedures to return more than one value. These proposals will be considered by the Scheme authors for inclusion in the Revised 5 Report on Scheme whenever that document comes up for discussion. For future columns, I am considering discussing other possible directions for Scheme language development, inc luding macros, dynamic binding, exception handling, modules, and concurrency. I may also do a column or two on Scheme compilation and interpretat ion techniques. If you've got an idea for some other topic you'd like me to discuss here, please feel free to write me at the addresses above; your suggestions are always welcome.