:: (c -> d) -> (a -> b -> c) -> a -> b -> d -package:pointless-fun -package:speculate -package:opaleye -package:composition-prelude
Compose two functions.
f .: g is similar to
f . g
except that
g will be fed
two arguments instead of one
before handing its result to
f.
This function is defined as
(f .: g) x y = f (g x y)
Example usage:
concatMap :: (a -> [b]) -> [a] -> [b]
concatMap = concat .: map
Notice how
two arguments (the function
and the list)
will be given to
map before the result is passed to
concat. This is equivalent to:
concatMap f xs = concat (map f xs)
Equivalent to
.:
The pattern of appending asterisks is straightforward to extend to
similar functions: (compose2 = .*, compose3 = .**, etc). However,
.: has been commonly adopted amongst Haskellers, and the need
for compose3 and beyond is rare in practice.
Compose composed with compose operator.
(f ... g) x y === f (g x y)
Multivariable composition.
f .: g ≡ (f .) . g ≡ \c d -> f (g c d)
Wrap the result of a function applied to 2 arguments.