[Haskell-cafe] Re: Very crazy
prionic at gmx.de
Tue Sep 25 09:18:24 EDT 2007
Dominic Steinitz schrieb:
> Andrew Coppin <andrewcoppin <at> btinternet.com> writes:
>> 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
> Look at the type of (.).(.) which should tell you how to compose functions
> with more than one variable. Mind you, I don't think it improves readability.
Interesting function. It got a sibling: (.)(.) :: (a1 -> b -> c) -> a1
-> (a -> b) -> a -> c
Anybody knows how to intepret that? I tried to call it with (++) "t"
(++"s") "it" but suddenly got distracted.
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the Haskell-Cafe