[Haskell-cafe] Re: (liftM join .) . mapM
dominic at steinitz.org
Tue Dec 29 16:09:46 EST 2009
Stephen Tetley <stephen.tetley <at> gmail.com> writes:
> -- | Compose an arity 1 function with an arity 2 function.
> -- B1 - blackbird
> oo :: (c -> d) -> (a -> b -> c) -> a -> b -> d
> oo f g = (f .) . g
> Extending the arity works quite nicely too:
> -- | Compose an arity 1 function with an arity 3 function.
> -- B2 - bunting
> ooo :: (d -> e) -> (a -> b -> c -> d) -> a -> b -> c -> e
> ooo f g = ((f .) .) . g
And oo = (.).(.) and ooo = (.).(.).(.)
There was a suggestion a few years back to standardise these as I recall
$0 = $
$1 = .
$2 = (.).(.)
and so on but nothing came of it.
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