[Haskell-cafe] Re: [Haskell] (.) . (.)

[Dominic Steinitz]

Brian Hulley wrote:

> Hi Dominic -
> I hope it's ok for me to ask this question and I'm absolutely burning 
> with curiosity to find out the answer...
> 
> How did you know to write ((.).(.)) instead of (\f g a b -> f (g a b)) ?

Brian,

I can't remember. I certainly don't find it intuitive. I think it was 
discussed on the Haskell mailing list a long time ago. Also I had a 
conversation with someone who pointed out that it's well known in 
combinatory logic. http://en.wikipedia.org/wiki/Combinatory_logic has a 
translation scheme from the lambda calculus to combinators. I presume 
that's how @pointless plugin in lambdabot works.

Dominic.