Unverified Commit be393db7 authored by Johannes Kirschbauer's avatar Johannes Kirschbauer Committed by GitHub
Browse files

lib.takeEnd: init (#398222)

parents 246969a0 9fee9e73

lib/default.nix

+1 −0
Original line number Diff line number Diff line
@@ -279,6 +279,7 @@ let 
        naturalSort

        compareLists

        take

        takeEnd

        drop

        dropEnd

        sublist

lib/lists.nix

+34 −0
Original line number Diff line number Diff line
@@ -1462,6 +1462,40 @@ rec { 
  */

  take = count: sublist 0 count;



  /**

    Return the last (at most) N elements of a list.



    # Inputs



    `count`



    : Maximum number of elements to pick



    `list`



    : Input list



    # Type



    ```

    takeEnd :: int -> [a] -> [a]

    ```



    # Examples

    :::{.example}

    ## `lib.lists.takeEnd` usage example



    ```nix

    takeEnd 2 [ "a" "b" "c" "d" ]

    => [ "c" "d" ]

    takeEnd 2 [ ]

    => [ ]

    ```



    :::

  */

  takeEnd = n: xs: drop (max 0 (length xs - n)) xs;



  /**

    Remove the first (at most) N elements of a list.

lib/tests/misc.nix

+63 −0
Original line number Diff line number Diff line
@@ -1357,6 +1357,69 @@ runTests { 
    )

  ];



  testTakeEnd =

    let

      inherit (lib) takeEnd;

    in

    testAllTrue [

      (

        takeEnd 0 [

          1

          2

          3

        ] == [ ]

      )

      (

        takeEnd 1 [

          1

          2

          3

        ] == [ 3 ]

      )

      (

        takeEnd 2 [

          1

          2

          3

        ] == [

          2

          3

        ]

      )

      (

        takeEnd 3 [

          1

          2

          3

        ] == [

          1

          2

          3

        ]

      )

      (

        takeEnd 4 [

          1

          2

          3

        ] == [

          1

          2

          3

        ]

      )

      (takeEnd 0 [ ] == [ ])

      (takeEnd 1 [ ] == [ ])

      (

        takeEnd (-1) [

          1

          2

          3

        ] == [ ]

      )

      (takeEnd (-1) [ ] == [ ])

    ];



  testDrop =

    let

      inherit (lib) drop;