I think that whitespace and alphanumeric should be disallowed. Not only would whitespace be confusing to use in this context, it would also mean that
# ifdef FOO
can't work, and we don't want that.
Otherwise, anything goes. In particular, there is an ample supply of Unicode characters to pick from. :-)
#! is special at the beginning of the first line, but having a string literal there would be a syntax error anyway, so I don't think overloading the syntax would lead to any particular problems.
/ Marcus Comstedt (ACROSS) (Hail Ilpalazzo!)
Previous text:
2003-09-21 22:57: Subject: Re: wish: string with other quoting then \
Yes, that's an idea.
So which characters after # can we allow for this? The whole non-alphabetical range, including space?
But numerical and ! is used already too, isn't it?
/ Mirar