Unverified Commit 24af4c04 authored by Silvan Mosberger's avatar Silvan Mosberger Committed by GitHub
Browse files

Merge pull request #214021 from tweag/ifilter0 

lib.lists.ifilter0: init
parents e41ca779 6861ef77

lib/default.nix

+1 −1
Original line number Diff line number Diff line
@@ -89,7 +89,7 @@ let 
      recurseIntoAttrs dontRecurseIntoAttrs cartesianProduct cartesianProductOfSets

      mapCartesianProduct updateManyAttrsByPath;

    inherit (self.lists) singleton forEach foldr fold foldl foldl' imap0 imap1

      concatMap flatten remove findSingle findFirst any all count

      ifilter0 concatMap flatten remove findSingle findFirst any all count

      optional optionals toList range replicate partition zipListsWith zipLists

      reverseList listDfs toposort sort sortOn naturalSort compareLists take

      drop sublist last init crossLists unique allUnique intersectLists

lib/lists.nix

+49 −1
Original line number Diff line number Diff line
@@ -4,7 +4,7 @@ 
{ lib }:

let

  inherit (lib.strings) toInt;

  inherit (lib.trivial) compare min id warn;

  inherit (lib.trivial) compare min id warn pipe;

  inherit (lib.attrsets) mapAttrs;

in

rec {
@@ -333,6 +333,54 @@ rec { 
  */

  imap1 = f: list: genList (n: f (n + 1) (elemAt list n)) (length list);



  /**

    Filter a list for elements that satisfy a predicate function.

    The predicate function is called with both the index and value for each element.

    It must return `true`/`false` to include/exclude a given element in the result.

    This function is strict in the result of the predicate function for each element.

    This function has O(n) complexity.



    Also see [`builtins.filter`](https://nixos.org/manual/nix/stable/language/builtins.html#builtins-filter) (available as `lib.lists.filter`),

    which can be used instead when the index isn't needed.



    # Inputs



    `ipred`



    : The predicate function, it takes two arguments:

      - 1. (int): the index of the element.

      - 2. (a): the value of the element.



      It must return `true`/`false` to include/exclude a given element from the result.



    `list`



    : The list to filter using the predicate.



    # Type

    ```

    ifilter0 :: (int -> a -> bool) -> [a] -> [a]

    ```



    # Examples

    :::{.example}

    ## `lib.lists.ifilter0` usage example



    ```nix

    ifilter0 (i: v: i == 0 || v > 2) [ 1 2 3 ]

    => [ 1 3 ]

    ```

    :::

  */

  ifilter0 =

    ipred:

    input:

    map (idx: elemAt input idx) (

      filter (idx: ipred idx (elemAt input idx)) (

        genList (x: x) (length input)

      )

    );



  /**

    Map and concatenate the result.

lib/tests/misc.nix

+27 −0
Original line number Diff line number Diff line
@@ -63,8 +63,10 @@ let 
    hasAttrByPath

    hasInfix

    id

    ifilter0

    isStorePath

    lazyDerivation

    length

    lists

    listToAttrs

    makeExtensible
@@ -651,6 +653,31 @@ runTests { 
    expected = ["b" "c"];

  };



  testIfilter0Example = {

    expr = ifilter0 (i: v: i == 0 || v > 2) [ 1 2 3 ];

    expected = [ 1 3 ];

  };

  testIfilter0Empty = {

    expr = ifilter0 (i: v: abort "shouldn't be evaluated!") [ ];

    expected = [ ];

  };

  testIfilter0IndexOnly = {

    expr = length (ifilter0 (i: v: mod i 2 == 0) [ (throw "0") (throw "1") (throw "2") (throw "3")]);

    expected = 2;

  };

  testIfilter0All = {

    expr = ifilter0 (i: v: true) [ 10 11 12 13 14 15 ];

    expected = [ 10 11 12 13 14 15 ];

  };

  testIfilter0First = {

    expr = ifilter0 (i: v: i == 0) [ 10 11 12 13 14 15 ];

    expected = [ 10 ];

  };

  testIfilter0Last = {

    expr = ifilter0 (i: v: i == 5) [ 10 11 12 13 14 15 ];

    expected = [ 15 ];

  };



  testFold =

    let

      f = op: fold: fold op 0 (range 0 100);