Module

Data.NonEmpty

Package: purescript-nonempty
Repository: purescript/purescript-nonempty

This module defines a generic non-empty data structure, which adds an additional element to any container type.

#NonEmpty Source

data NonEmpty :: (Type -> Type) -> Type -> Typedata NonEmpty f a

A non-empty container of elements of type a.

import Data.NonEmpty

nonEmptyArray :: NonEmpty Array Int
nonEmptyArray = NonEmpty 1 [2,3]

import Data.List(List(..), (:))

nonEmptyList :: NonEmpty List Int
nonEmptyList = NonEmpty 1 (2 : 3 : Nil)

Constructors

NonEmpty a (f a)

Instances

(Show a, Show (f a)) => Show (NonEmpty f a)
(Eq1 f, Eq a) => Eq (NonEmpty f a)
(Eq1 f) => Eq1 (NonEmpty f)
(Ord1 f, Ord a) => Ord (NonEmpty f a)
(Ord1 f) => Ord1 (NonEmpty f)
(Functor f) => Functor (NonEmpty f)
(FunctorWithIndex i f) => FunctorWithIndex (Maybe i) (NonEmpty f)
(Foldable f) => Foldable (NonEmpty f)
(FoldableWithIndex i f) => FoldableWithIndex (Maybe i) (NonEmpty f)
(Traversable f) => Traversable (NonEmpty f)
(TraversableWithIndex i f) => TraversableWithIndex (Maybe i) (NonEmpty f)
(Foldable f) => Foldable1 (NonEmpty f)
(Unfoldable f) => Unfoldable1 (NonEmpty f)
(Applicative f, Semigroup (f a)) => Semigroup (NonEmpty f a)
This is a lawful Semigroup instance that will behave sensibly for common nonempty containers like lists and arrays. However, it's not guaranteed that pure will behave sensibly alongside <> for all types, as we don't have any laws which govern their behavior.

#singleton Source

singleton :: forall f a. Plus f => a -> NonEmpty f a

Create a non-empty structure with a single value.

import Prelude

singleton 1 == 1 :| []
singleton 1 == 1 :| Nil

#(:|) Source

Operator alias for Data.NonEmpty.NonEmpty (right-associative / precedence 5)

An infix synonym for NonEmpty.

nonEmptyArray :: NonEmpty Array Int
nonEmptyArray = 1 :| [2,3]

nonEmptyList :: NonEmpty List Int
nonEmptyList = 1 :| 2 : 3 : Nil

#foldl1 Source

foldl1 :: forall f a. Foldable f => (a -> a -> a) -> NonEmpty f a -> a

Fold a non-empty structure, collecting results using a binary operation.

foldl1 (+) (1 :| [2, 3]) == 6

#fromNonEmpty Source

fromNonEmpty :: forall f a r. (a -> f a -> r) -> NonEmpty f a -> r

Apply a function that takes the first element and remaining elements as arguments to a non-empty container.

For example, return the remaining elements multiplied by the first element:

fromNonEmpty (\x xs -> map (_ * x) xs) (3 :| [2, 1]) == [6, 3]

#oneOf Source

oneOf :: forall f a. Alternative f => NonEmpty f a -> f a

Returns the alt (<|>) result of:

The first element lifted to the container of the remaining elements.
The remaining elements.

import Data.Maybe(Maybe(..))

oneOf (1 :| Nothing) == Just 1
oneOf (1 :| Just 2) == Just 1

oneOf (1 :| [2, 3]) == [1,2,3]

#head Source

head :: forall f a. NonEmpty f a -> a

Get the 'first' element of a non-empty container.

head (1 :| [2, 3]) == 1

#tail Source

tail :: forall f a. NonEmpty f a -> f a

Get everything but the 'first' element of a non-empty container.

tail (1 :| [2, 3]) == [2, 3]

Modules: Data.NonEmpty