Comments on: Generalizing (.)

By: Edward Kmett

Edward Kmett — Fri, 11 Mar 2011 20:02:18 +0000

Paul:

Back when I wrote this post I gave the updated (.) the wrong precedence, it should be

infixr 9 .

By: Paul Keir

Paul Keir — Fri, 11 Mar 2011 12:44:52 +0000

Another great post and really neat idea. I tried
((+2) . (*3)) 5
and also
((+2) . (*3)) $ 5
but this
(+2) . (*3) $ 5
complains about a missing Num instance for the literal ‘5′. It makes me wonder why the 5 is accepted in any case, as it’s not (here at least) an instance of Functor?

By: Edward Kmett

Edward Kmett — Tue, 24 Jul 2007 15:05:25 +0000

Thanks. Fixed.

I honestly, just typed that off the cuff.

Thats what I get for not actually compiling it before posting ;)

By: Fritz

Fritz — Tue, 24 Jul 2007 07:58:47 +0000

I think you need doubled parens when hiding (.) in the import (the outer ones are part of the hiding syntax, the inner ones refer to the infix composition symbol in parens for lexical reasons). Both hugs and ghci seem to like it this way. (Perhaps something in your text chain snarfed the “redundant” parens?)

By: mgsloan

mgsloan — Thu, 01 Feb 2007 07:15:09 +0000

PS, I don’t think it’d be too hard for noobs to learn it. When I was a noob I wondered why this didn’t work!

By: mgsloan

mgsloan — Thu, 01 Feb 2007 07:14:16 +0000

This was added to The Other Prelude (perhaps one of the reasons it was created).

http://www.haskell.org/haskellwiki/The_Other_Prelude

Probably inspired by your irc golfings.

By: Edward Kmett

Edward Kmett — Thu, 09 Nov 2006 06:22:54 +0000

As an aside, the idea came from observing the fact that lambdabot's pointfree conversion command @pl had taken to using `fmap` instead of (.) in a lot of places.