[Haskell-cafe] Re: (liftM join .) . mapM

Stephen Tetley 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 something like: $0 = $ $1 = . $2 = (.).(.) and so on but nothing came of it. Dominic.