lib.takeEnd: init (#398222)

lib/default.nix

@@ -279,6 +279,7 @@ let
         naturalSort
         compareLists
         take
+        takeEnd
         drop
         dropEnd
         sublist

lib/lists.nix

@@ -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

@@ -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;