[Haskell-beginners] difference between . and $

[Rafael Gustavo da Cunha Pereira Pinto]

No, not really

the '.' operator is function composition, so f.g is a new function with f
applied over g.

h=f.g ==> h x = f ( g x )

the '$' is the apply operator, and it applies the right side to the left
side:

h = f $ x ==> h= f ( x )


You can check this looking at their types

(.) :: (b -> c) -> (a -> b) -> a -> c
($) :: (a -> b) -> a -> b

the first one takes two functions and return a new function. The second
takes a function and a value and returns a value.

Regards

Rafael

On Sun, Oct 30, 2011 at 15:39, <haxl at nym.hush.com> wrote:

> Doesn't . and $ do the same thing?  I always get confused about
> that, like when would I use one over the other.
>
>
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-- 
Rafael Gustavo da Cunha Pereira Pinto
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