### pointless-fun 1.1.0

The pointless-fun package offers some common point-free combinators (common for me at least).

### Description

Perhaps the most useful is that it packages up Matt Hellige's classic multicomposition trick[1]. These combinators allow you to easily modify the types of a many-argument function with syntax that looks like giving type signatures. For example,

foo :: A -> B -> C
albert :: X -> A
beth :: Y -> B
carol :: C -> Z
bar :: X -> Y -> Z
bar = foo $:: albert ~> beth ~> carol

I've found this to be especially helpful for defining non-derivable type class instances for newtypes since it both abstracts away the plumbing and also makes explicit what you mean.

Other prevalent combinators include, `(.:)`

for binary composition:

(f .: g) x y = f (g x y)
-- or,
f .: g = curry (f . uncurry g)

This is the same as the common idiom `(f .) . g`

but more easily extended to multiple uses, due to the fixity declaration.

And `(.!)`

for function composition which calls the right-hand function eagerly; i.e., making the left-hand function strict in its first argument.

(f .! g) x = f $! g x

This defines the composition for the sub-category of strict Haskell functions. If the `Functor`

class were parameterized by the domain and codomain categories (e.g., a regular `Functor f`

would be `CFunctor (->) (->) f`

instead) then this would allow us to define functors `CFunctor (->) (!->) f`

where `fmap f . fmap g = fmap (f .! g)`

[1] http://matt.immute.net/content/

### Links

- Homepage: http://code.haskell.org/~wren/
- Hackage: http://hackage.haskell.org/package/
pointless-fun - Darcs: http://community.haskell.org/~wren/
pointless-fun - Haddock: Darcs version