Copyright | Nils Anders Danielsson 2006 Alexander Berntsen 2014 |
---|---|
License | BSD-style (see the LICENSE file in the distribution) |
Maintainer | [email protected] |
Stability | experimental |
Portability | portable |
Safe Haskell | Trustworthy |
Language | Haskell2010 |
Simple combinators working solely on and with functions.
Identity function.
const x
is a unary function which evaluates to x
for all inputs.
For instance,
>>>
map (const 42) [0..3]
[42,42,42,42]
(.) :: (b -> c) -> (a -> b) -> a -> c infixr 9 Source
Function composition.
flip :: (a -> b -> c) -> b -> a -> c Source
flip f
takes its (first) two arguments in the reverse order of f
.
($) :: (a -> b) -> a -> b infixr 0 Source
Application operator. This operator is redundant, since ordinary application (f x)
means the same as (f $ x)
. However, $
has low, right-associative binding precedence, so it sometimes allows parentheses to be omitted; for example:
f $ g $ h x = f (g (h x))
It is also useful in higher-order situations, such as map ($ 0) xs
, or zipWith ($) fs xs
.
(&) :: a -> (a -> b) -> b infixl 1 Source
&
is a reverse application operator. This provides notational convenience. Its precedence is one higher than that of the forward application operator $
, which allows &
to be nested in $
.
Since: 4.8.0.0
fix f
is the least fixed point of the function f
, i.e. the least defined x
such that f x = x
.
on :: (b -> b -> c) -> (a -> b) -> a -> a -> c infixl 0 Source
(*) `on` f = \x y -> f x * f y
.
Typical usage: sortBy (compare `on` fst)
.
Algebraic properties:
© The University of Glasgow and others
Licensed under a BSD-style license (see top of the page).
https://downloads.haskell.org/~ghc/8.2.1/docs/html/libraries/base-4.10.0.0/Data-Function.html