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Re: what are #!KEY &c.?
On 11-Apr-06, at 3:32 PM, Taylor R. Campbell wrote:
Are these symbols? Keywords? A wholly new, disjoint type of data? I
can't find this in the specification; there's only a brief remark
about it in the section on implementation, but this is very important
since these are otherwise ill-defined data in S-expressions.
The only requirement is that #!optional, #!key and #!rest be distinct
objects (i.e. not eqv? to anything else). The #!foo syntax adopted
by DSSSL is probably inspired from the R2RS which had the #!true, #!
false, and #!null syntax for true, false and the empty list. Some
Scheme systems still use the #!foo syntax for some objects (Gambit
and Chez Scheme use #!eof to denote the end-of-file object).