Copyright | (c) Gershom Bazerman 2018 |
---|---|

License | BSD-style |

Maintainer | [email protected] |

Portability | portable |

Safe Haskell | Trustworthy |

Language | Haskell98 |

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`

.

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.

`nubOrd`

is strict in the elements of the list.

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.

`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.

`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.

`nubIntOn`

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

© The University of Glasgow and others

Licensed under a BSD-style license (see top of the page).

https://downloads.haskell.org/~ghc/8.8.3/docs/html/libraries/containers-0.6.2.1/Data-Containers-ListUtils.html