David Kastrup <d...@gnu.org> writes: > Mark H Weaver <m...@netris.org> writes: > >> David Kastrup <d...@gnu.org> writes: >>> I guess my "real" problem is that I'd like to do call wrapping by writing >>> >>> (lambda ( . x) (fun . x)) >>> >>> instead of having to write >>> >>> (lambda ( . x) (apply fun x)) >>> >>> I assume eval is not supposed to try dealing with dotted lists? >> >> The problem is that (f . (g x y)) is equivalent to (f g x y). >> Therefore, while Scheme could in theory support procedure calls with a >> dotted tail that happened to be an atom, it would do something rather >> different and confusing if the dotted tail was itself a procedure/macro >> call. > > A list in dotted tail position is evaluated via (map ... eval) rather > than (eval ...). I don't see much of a problem with that. > > It works fine for () as one can see: > guile> (+ . ()) > 0 > guile> > > So why not for others?
I'll answer this a bit myself. Well, it does work for other lists. Cough, cough. The question is why it doesn't for non-lists. If (f . x) was supposed to be equivalent to (apply f x), then x would need to be evaluated. In (+ . ()), () itself is _not_ being evaluated. So this would be new behavior, and at least different from that of the non-pair (). I'm still not convinced that it would be a bad idea... -- David Kastrup
