[Haskell-cafe] Re: Re-order type (flip map)
Ozgur Akgun
ozgurakgun at gmail.com
Sun Oct 10 18:47:45 EDT 2010
On 10 October 2010 22:32, Johannes Waldmann <waldmann at imn.htwk-leipzig.de>wrote:
> Oh, and while we're at it - are there standard notations
> for "forward" function composition and application?
>
> I mean instead of h . g . f $ x
> I'd sometimes prefer x ? f ? g ? h
> but what are the "?"
>
While asking you use the same symbol for function composition, and something
like inverse function application. I don't think there exists an operator ?,
such that h . g . f $ x is equivalent to x ? f ? g ? h.
But you can simply define an inverse function application like the following
and have a close enough alternative,
($$) :: a -> (a -> b) -> b
($$) = flip ($)
infixl 5 $$
Now the following two expression are identical, I suppose:
h . g . f $ x
x $$ f . g . h
Cheers,
Ozgur
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