Hi Ludovic, On Mon 16 Mar 2009 23:16, l...@gnu.org (Ludovic Courtès) writes:
> scheme@(guile-user)> ,o interp #t > scheme@(guile-user)> (define v (values 0 1 2 3)) Here you enter territory that is explicitly undefined by the Scheme spec (R5 and R6, I think). > scheme@(guile-user)> ,o interp #f > scheme@(guile-user)> (define v (values 0 1 2 3)) Here as well. What the VM does was a conscious decision, to discard extra values. So `v' is now 0. > scheme@(guile-user)> (let-values (((a b c d) v)) (list a b c d)) And obviously v is not a MV-producing expression. > OTOH, I suspect that the effect of storing multiple values in a single > variable is not specified anyway. (FWIW, Bigloo discards all values but > the first and Ikarus throws an error.) There are two things that an implementation might sensibly choose to do when more values than expected are returned to a continuation: - Error. - Truncate the values to the number that was expected. Guile does neither :) Which has its uses, I guess, but it prevents efficient implementation. On the VM, returning multiple values is really cheap. There's no consing involved. So I would say about this: we can probably deal with it. It's unspecified anyway, and is really an edge case. Happy hacking, Andy -- http://wingolog.org/
