Re: Flipped function application

On Thu, Oct 10, 2013 at 10:13 AM, Dan Doel wrote:

On Thu, Oct 10, 2013 at 4:46 AM, Simon Peyton-Jones wrote:

...

F# uses (|>). Maybe (#) is good. To me (&) looks too commutative because it’s usually used for conjunction.

I mentioned this on the core list, but I'll mention it here, too:

I don't like (|>), because once you have this operator, you also might as well have the functorial version. We have ($) and (<$>), and lens has (&) and (<&>). The latter is useful for functorial 'for blocks':

myFunctorValue <&> \x -> ...complex expression...

I actually think it's (significantly) more useful than (&). But, I think (<|>>) is a pretty awful name for it, so I'd prefer a name that makes both palatable.

I'm still not convinced we need flipped application in general[1], and I'm sure we don't need new name suggestions at this point, but: Consider <**> :: f a -> f (a -> b) -> f b. That suggests <$$> :: f a -> (a -> b) -> f b by analogy, so maybe $$ :: a -> (a -> b) -> b? This avoids the downsides of & while maybe being less ugly to combine with things than |>. Also, it looks like $, suggesting they're related. [1]: Although it's certainly convenient for some idioms, like working with lenses. -- Dave Menendez http://www.eyrie.org/~zednenem/