Hi Josef, I seem to be the negative guy in replies to you. Apologies for that!
On Mon 22 Mar 2010 20:25, Josef Wolf <j...@raven.inka.de> writes: > On Fri, Mar 19, 2010 at 08:54:02AM -0400, Ken Raeburn wrote: >> >> The result of (if #f #f) is unspecified, not #f, according to r5rs. >> That means an implementation can produce whatever value it wants. In the R6RS, evaluating `(if #f #f)' returns "unspecified values" -- that is, even the number of values is unspecified. And in fact it would make sense for `(if #f #f)' to be the same as `(values)' -- an expression returning zero values. > I think I like this type of "unspecified". Much better than the > "undefined behavior" definition in C. Unfortunately it really is unspecified :) OK it's better than C, in the sense that it won't launch the missiles, but it would be better if evaluating: (+ 2 (if #f #f)) yielded an error of "too few values to continuation" rather than "don't know how to add #<unspecified>". Cheers, Andy -- http://wingolog.org/
