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whether #!identifiers are datums



This isn't very relevant to SRFI 103, but it comes up
from time to time.

Derick Eddington wrote:
> I thought #!identifier lexical tokens are considered comments at a level
> below "syntactic datums".  I, of course, meant the first thing the
> standard read procedure would return.  I thought calling that a "datum"
> was the normal terminology.

#!r6rs is the only lexical token of that form that is
guaranteed to be a comment.  Tokens such as #!undefined
and #!eof are unlikely to be comments in implementations
that support such things.

In R6RS systems, whether implementation-dependent directives
like #!fold-case and #!no-fold-case are comments is also
implementation-dependent.  In ERR5RS, those directives are
datums, not comments, and apply only to the port from which
they are read; if someone wants to change the case-folding
mode for a port without adding a datum, one of those tokens
can be preceded by a #; token.  See the end of
http://scheme-punks.org/wiki/index.php?title=ERR5RS:Lexical_Syntax

Will