Keywords look like :foo, foo:, or #:foo, depending on the Scheme implementation:
- Gauche (and Common Lisp) support :foo.
- Gambit, Kawa (and DSSSL) support foo:.
- Bigloo supports both foo: and :foo and treats them as the same (in the sense of eqv?).
- Scheme 7 supports both foo: and :foo and treats them as distinct (in the sense of eqv?).
- MZScheme, Guile support #:foo.
- Chicken supports #:foo always, and also allows either foo: or :foo depending on the setting of a parameter or a startup option.
- MIT, Scheme48/scsh, SISC, Chez, SCM, Ikarus, Larceny, Mosh, Scheme 9, SSCM, SXM, VSCM, Chibi don't support any of them.