On Thu 19 May 2011 20:50, Jim Rees <jimreesma@gmail.com> writes:

>     (let ((x (if #f 'never))) <stuff that does not depend on x>)
>
> is legal Scheme code (based on the interpretation that initializers
> *must* return a single value, unspecified or not).

It is currently legal.  It runs on all systems that implement R5RS.  If
the the final Scheme 2011 came out tomorrow and it said that (if #f #f)
is "unspecified values" instead of "an unspecified value", then the
program still runs on those implementations.

However, it was never in good taste, not even now, before the new report
is out.

> I know nothing about the existing code that depends on this particular
> feature.   I would personally have preferred "any number", as it's
> handy for detecting buggy code.

Yeah, dunno.  But there are oodles of implementations out there.  If
someone needs this feature from their old program so badly, then they
can choose one of the vast majority of implementations that will
actually produce one single value.

MHO anyway :)

Andy
--
http://wingolog.org/

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