containers-0.6.2.1: Assorted concrete container types

Copyright | (c) Gershom Bazerman 2018
License | BSD-style
Maintainer | libraries@haskell.org
Portability | portable
Safe Haskell | Trustworthy
Language | Haskell98

Data.Containers.ListUtils

Description

This module provides efficient containers-based functions on the list type.

In the documentation, \(n\) is the number of elements in the list while \(d\) is the number of distinct elements in the list. \(W\) is the number of bits in an `Int`.

Synopsis

- nubOrd :: Ord a => [a] -> [a]
- nubOrdOn :: Ord b => (a -> b) -> [a] -> [a]
- nubInt :: [Int] -> [Int]
- nubIntOn :: (a -> Int) -> [a] -> [a]

# Documentation

nubOrd :: Ord a => [a] -> [a] Source #

\( O(n \log d) \). The `nubOrd` function removes duplicate elements from a list. In particular, it keeps only the first occurrence of each element. By using a `Set` internally it has better asymptotics than the standard `nub` function.

#### Strictness

`nubOrd` is strict in the elements of the list.

#### Efficiency note

When applicable, it is almost always better to use `nubInt` or `nubIntOn` instead of this function, although it can be a little worse in certain pathological cases. For example, to nub a list of characters, use

     nubIntOn fromEnum xs

nubOrdOn :: Ord b => (a -> b) -> [a] -> [a] Source #

The `nubOrdOn` function behaves just like `nubOrd` except it performs comparisons not on the original datatype, but a user-specified projection from that datatype.

#### Strictness

`nubOrdOn` is strict in the values of the function applied to the elements of the list.

nubInt :: [Int] -> [Int] Source #

\( O(n \min(d,W)) \). The `nubInt` function removes duplicate `Int` values from a list. In particular, it keeps only the first occurrence of each element. By using an `IntSet` internally, it attains better asymptotics than the standard `nub` function.

See also `nubIntOn`, a more widely applicable generalization.

#### Strictness

`nubInt` is strict in the elements of the list.

nubIntOn :: (a -> Int) -> [a] -> [a] Source #

The `nubIntOn` function behaves just like `nubInt` except it performs comparisons not on the original datatype, but a user-specified projection from that datatype. For example, `nubIntOn `fromEnum`` can be used to nub characters and typical fixed-with numerical types efficiently.

#### Strictness

`nubIntOn` is strict in the values of the function applied to the elements of the list.