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On 14-Apr-06, at 9:57 AM, John Cowan wrote:
I'll add something in the preamble saying: The tokens of the form ``foo:'' used in this document will be called ``keywords''. On Scheme implementations supporting SRFI 88, these keywords correspond to the keyword objects specified in that SRFI. On Scheme implementations which do not support SRFI 88, these keywords are symbols.Which is as much as to say that they need to be quoted on non-SRFI-88 systems, as your followup notes. This is always a safe strategy, since a quoted keyword evaluates to itself. Keywords are controversial (if nobody else, I am making controversy about them!), and this otherwise satisfactory SRFI should not, IMHO, depend on their presence.
I could add to the spec thatOn Scheme implementations that do not support SRFI 88, the variables ``direction:'', ``char-encoding:'', etc are defined to evaluate to the symbol of the same name. That is
(define direction: 'direction:)
(define char-encoding: 'char-encoding:)
...
This way these ``keywords'' don't have to be quoted, regardless of
support for SRFI 88.
I'll have to think about this some more but currently I don't see a problem with that.
Marc