On Wed, Jul 15, 2009 at 3:08 AM, Hans Aberg <hab...@math.su.se> wrote:
> On 15 Jul 2009, at 12:25, Eugene Kirpichov wrote: > > If ++ could be pattern matched, what should have been the result of >> "let (x++y)=[1,2,3] in (x,y)"? >> > > It will branch. In terms of unification, you get a list of substitutions. f :: [a] -> ([a],[a]) f (x ++ y) = (x,y) If this pattern branches, it could hardly be considered a *function *which takes lists and returns pairs. It would have to return something else. Luke
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