between-0.9.0.2: README.md
Between
=======
[][Hackage: between]
Description
-----------
It turns out that this combinator
f ~@~ g = (f .) . (. g)
is a powerful thing. It was abstracted from following (commonly used)
pattern `f . h . g` where `f` and `g` are fixed.
This library not only define `~@~` combinator, but also some derived
combinators that can help us to easily define a lot of things including
lenses. See [lens package][Hackage: lens] for detais on what lenses are.
Function `Data.Function.on` can be implemented using `~@~` as:
on :: (b -> b -> c) -> (a -> b) -> a -> a -> c
on f g = (id ~@~ g ~@~ g) f
If function @on3@ existed in /base/ then it could be defined as:
on3 :: (b -> b -> b -> d) -> (a -> b) -> a -> a -> a -> d
on3 f g = (id ~@~ g ~@~ g ~@~ g) f
For more examples see documentation.
Documentation
-------------
Stable releases with API documentation are available on
[Hackage][Hackage: between].
Contributions
-------------
Contributions, pull requests and bug reports are welcome! Please don't be
afraid to contact author using GitHub or by e-mail (see `.cabal` file for
that).
[Hackage: between]:
https://hackage.haskell.org/package/between
[Hackage: lens]:
http://hackage.haskell.org/package/lens