between: Function combinator "between" and derived combinators

[ bsd3, data, library ] [ Propose Tags ]

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 defines ~@~ combinator, but also some derived combinators that can help us easily define a lot of things including lenses. See lens package 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

Other usage examples and documentation can be found in Data.Function.Between module.

Versions [RSS] [faq] 0.9.0.0, 0.9.0.1, 0.9.0.2, 0.10.0.0, 0.11.0.0 ChangeLog.md base (>3 && <5) [details] BSD-3-Clause (c) 2013-2016, Peter Trško Peter Trško peter.trsko@gmail.com Data https://github.com/trskop/between https://github.com/trskop/between/issues head: git clone git://github.com/trskop/between.gitthis: git clone git://github.com/trskop/between.git(tag v0.11.0.0) by PeterTrsko at 2016-01-09T12:06:16Z LTSHaskell:0.11.0.0, NixOS:0.11.0.0, Stackage:0.11.0.0 4110 total (55 in the last 30 days) (no votes yet) [estimated by Bayesian average] λ λ λ Docs available Last success reported on 2016-01-09

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pedantic

Pass additional warning flags to GHC.

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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 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.

Building Options

• -fpedantic (disabled by default)

Pass additional warning flags to GHC.

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).