Am Dienstag, 19. Februar 2008 18:26 schrieben Sie:
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However, I was told this: ~> a b is a ~> b, but if I write c a b and wish the effect of a `c` b. This would not work. ~> as an infix operator has a special place in GHC. It is not "just a type variable".
Sorry, but I don’t understand fully what you mean. :-( But nevertheless, a ~> b is not the same as ~> a b but as (~>) a b. It’s just like with ordinary operators where a + b is the same as (+) a b. ~> is not special in GHC. You could use, for example, ### instead of ~> and get the same results. However, GHC accepts type operators only if you tell it to do so. Give GHC the option -XTypeOperators or insert {-# LANGUAGE TypeOperators #-} at the beginning of your source file.
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Best wishes, Wolfgang