<div>On 12/24/06, Carl Eastlund <<a href="mailto:cce@ccs.neu.edu">cce@ccs.neu.edu</a>> wrote:<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> On 12/24/06, Corey Sweeney <<a href="mailto:corey.sweeney@gmail.com">corey.sweeney@gmail.com</a>> wrote: > > And the rest prefer not to construct an arbitrary, irrelevant syntax so they > use lists ;) > > But I do see your point.  I can now see why some people are using > multi-value's.  But I would argue that it should be a compiler thing, not a > syntax thing. Scheme has multiple inputs without resorting to lists (for functions of fixed input size), so having the same thing for outputs isn't really arbitrary or irrelevant. </blockquote><div> heh.  Multiple inputs is generally a arbitrary syntax too.  I basically see "(define (my-function a b c) {blah}))" as syntactic sugar for: "(define my-function (lambda (a) (lambda (b) (labmda (c) {blah}))))" Your function "{blah}" works the same either way.  Also "(my-function x y z)" would be syntacitic sugar for "(((my-function x) y) z)". The only differnce from the users perspective is that when implemented as "multi input values syntax" instead of a "bunch of lambdas syntax", then the interpreter can check for arity errors when calling.  I.E.  in the "bunch of lambdas syntax" method, (define add-two (+ 2)) becomes a valid function, but in the multi input values syntax method (define add-two (+ 2)) throws a arity error and says that it can't work without 2 parameters, so you need to do:  (define add-two (lambda (x) (+ 2 x))). However I usually use the "multi value syntax", because in normal R5RS intrepeters, "(my-function x y z)" is not syntacitic sugar for "(((my-function x) y) z)". in the "bunch of lambda functions syntax" any result list of length 3 or less can be "folded" into my-function.  in "multi input values syntax" you get arity errors. </div> <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> Lists (linear, arbitrary-size, usually homogenous data structures), on the other hand, are not a close fit (for flat, fixed-size, often heterogenous function outputs). Anyway, this isn't (just) an efficiency issue.  It's a matter of what the programmer can express.  Multiple values says "this program outputs these two things".  Lists say "this program outputs a list".</blockquote><div> I think were settled on the effiency issue, but I'm not seeing the non-effencity issue in this one.  Are you saying that when i have a set of numbers, that i'm actually saying "i have a set of numbers, not a list of numbers with special set properties added to them"?  I.E. like we should add set as a new primative because I want to name it differntly then "list of numbers with special set properties"?  If we've discarded effencicy issues, then we shouldn't need such a thing, right? Corey  </div> <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Multiple values aren't my favorite program construct either, but I think we've covered the ground of why they exist as they are. -- Carl Eastlund </blockquote></div> -- ((lambda (y) (y y)) (lambda (y) (y y)))