Module

Data.Function

Package
purescript-prelude
Repository
purescript/purescript-prelude

#flipSource

flip :: forall a b c. (a -> b -> c) -> b -> a -> c

Flips the order of the arguments to a function of two arguments.

flip const 1 2 = const 2 1 = 2

#constSource

const :: forall a b. a -> b -> a

Returns its first argument and ignores its second.

const 1 "hello" = 1

#applySource

apply :: forall a b. (a -> b) -> a -> b

Applies a function to an argument. This is primarily used as the operator ($) which allows parentheses to be omitted in some cases, or as a natural way to apply a chain of composed functions to a value.

#($)Source

Operator alias for Data.Function.apply (right-associative / precedence 0)

Applies a function to an argument: the reverse of (#).

length $ groupBy productCategory $ filter isInStock $ products

is equivalent to:

length (groupBy productCategory (filter isInStock products))

Or another alternative equivalent, applying chain of composed functions to a value:

length <<< groupBy productCategory <<< filter isInStock $ products

#applyFlippedSource

applyFlipped :: forall a b. a -> (a -> b) -> b

Applies an argument to a function. This is primarily used as the (#) operator, which allows parentheses to be ommitted in some cases, or as a natural way to apply a value to a chain of composed functions.

#(#)Source

Operator alias for Data.Function.applyFlipped (left-associative / precedence 1)

Applies an argument to a function: the reverse of ($).

products # filter isInStock # groupBy productCategory # length

is equivalent to:

length (groupBy productCategory (filter isInStock products))

Or another alternative equivalent, applying a value to a chain of composed functions:

products # filter isInStock >>> groupBy productCategory >>> length

#onSource

on :: forall a b c. (b -> b -> c) -> (a -> b) -> a -> a -> c

The on function is used to change the domain of a binary operator.

For example, we can create a function which compares two records based on the values of their x properties:

compareX :: forall r. { x :: Number | r } -> { x :: Number | r } -> Ordering
compareX = compare `on` _.x

Re-exports from Control.Category

#compose

compose :: forall b c d a. Semigroupoid a => a c d -> a b c -> a b d

#id

id :: forall t a. Category a => a t t

#(>>>)Source

Operator alias for Control.Semigroupoid.composeFlipped (right-associative / precedence 9)

#(<<<)Source

Operator alias for Control.Semigroupoid.compose (right-associative / precedence 9)