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Re: Proposed mildly incompatible change to MULTIPLE-VALUE(-BIND)
- To: Guy.Steele at CMU-10A
- Subject: Re: Proposed mildly incompatible change to MULTIPLE-VALUE(-BIND)
- From: David A. Moon <MOON at MIT-MC>
- Date: Fri ,17 Apr 81 22:53:00 EDT
- Cc: LISP-FORUM at MIT-MC, Scott.Fahlman at CMU-10A
This sounds superficially plausible and has been proposed many times before.
The reason it has never been accepted is that in practice most functions
which return multiple values rely on the feature that extra values the
caller does not want are thrown away. Calling and returning aren't really
as symmetric in practice as they are in theory. It probably would be useful
to have a way of requiring at least a certain number of values to be
returned. Of course, then all the functions which rely on extra values
being supplied NIL would have to be fixed. This is pretty common practice
when you have code like (and <condition> (values <val1> <val2>)).