[Haskell-cafe] Syntax proposal for "reverse apply"/"pipeline apply" (flip ($))

[Taylor Hedberg]

lens defines & for this purpose (not that one would want to pull in the
behemoth that is lens as a dependency just for that).


On Wed, Apr 16, 2014 at 3:25 PM, Alexey Muranov <alexey.muranov at gmail.com>wrote:

> Hello,
>
> i am completely new to Haskell, but i am somewhat fascinated by
> lambda-calculus and programming.
>
> For whatever it is worth, i would like to propose for discussion a syntax
> for "(flip ($))" operation in Haskell.
>
> I think that a good syntax would be "|^", for example:
>
>     square x = x * x
>     y = 3 |^ square             -- y == 9
>
>
> Explanation:
>
> * i would have suggested just ^, but it would conflict with number
> exponentiation,
>
> * it is rather common in mathematics to write function application in
> exponential notation:  x ^ f  instead of  f(x), especially if  f  is an
> automorphism of some structure,
>
> * (flip ($)) is exactly the exponentiation of Church numerals,
>
> * in "The calculi of lambda-conversion", Alonzo Church uses the
> "shorthand" notation "[N^M]" for "(MN)", where M and N are lambda-terms.
>
> * I am probably not the only person missing the ability to apply functions
> from the right:
>
> http://stackoverflow.com/questions/1457140/haskell-composition-vs-fs-pipe-forward-operator
>
> Well, other notations i've thought of are "\^" and "~$".
>
> Alexey.
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