On 2007-09-25, Andrew Coppin
I just found it rather surprising. Every time *I* try to compose with functions of more than 1 argument, the type checker complains. Specifically, suppose you have
foo = f3 . f2 . f1
Assuming those are all 1-argument functions, it works great. But if f1 is a *two* argument function (like map is), the type checker refuses to allow it, and I have to rewrite it as
foo x y = f3 $ f2 $ f1 x y
which is really extremely annoying...
I'm just curiose as to why the type checker won't let *me* do it, but it will let *you* do it. (Maybe it hates me?)
Don't anthropomorphize computers. They hate it when you do that. I'm guessing the problem is probably incorrect parenthesizing. foo x y = f3 . f2 . f1 x y won't typecheck, but foo x y = (f3 . f2 . f1) x y should. Function application is the highest precedence, so the first definition is parsed as foo x y = f3 . f2 . (f1 x y) which will only type-check if f1 has 3 or more arguments, as (f1 x y) must be a function. The trickier parts are more than 1 argument functions as the first argument to (.). Are you sure your failed attempts weren't of this form? -- Aaron Denney -><-