[Haskell-beginners] f . g or f g or f $ g?

[Mateusz Kowalczyk]

A less obvious interpretation is to treat ($) as `id'.

 (f . g) x = f $ g x = f (id g x) = f (g x)

Bah, we can even illustrate that ($) is simply an infix identity function:
Prelude> map ((flip id) 2) [\x -> x - 3]
[-1]
Prelude> map (`id` 2) [\x -> x - 3]
[-1]
Prelude> map ($ 2) [\x -> x - 3]
[-1]


I just wanted to throw this out there as I found this out recently
myself and found it fairly useful. I believe someone else already posted
a link about pointless style.

On 12/02/13 21:09, Martin Drautzburg wrote:
> On Friday, 1. February 2013 23:02:39 Ertugrul Söylemez wrote:
> 
>>     (f . g) x = f (g x)
> 
> 
> so (f . g) x = f $ g x
> 
> right?
> 
> That looks like the two are pretty interchangeable. When would I prefer one 
> over the other?
> 
>