Add take() function

README.md

@@ -106,6 +106,7 @@ The target can be any expression. It will be passed as the first argument to the
 | `contains` | Returns whether a list contains a value                     | `foo:list<string>.contains:bool("bar")`          |
 | `some`     | Returns whether any element matches a [predicate](#lambdas) | `foo:list<int>.some:bool(\|item\| item:int > 5)` |
 | `substr`   | Returns a substring of a string                             | `foo:string.substr:string(0, 5)`                 |
+| `take`     | Returns the first n elements of a list                      | `foo:list<string>.take:list<string>(5)`          |
 
 #### Custom Functions
 

src/Scope.php

@@ -11,6 +11,7 @@
 use function array_is_list;
 use function array_keys;
 use function array_map;
+use function array_slice;
 use function array_values;
 use function count;
 use function get_debug_type;
@@ -44,6 +45,7 @@ public function __construct(private readonly array $vars = [], array $funcs = []
             'filter' => self::filter(...),
             'some' => self::some(...),
             'substr' => substr(...),
+            'take' => self::take(...),
         ] : [];
         $shadowed = array_intersect(array_keys($predefinedFuncs), array_keys($funcs));
         if ($shadowed !== []) {
@@ -126,6 +128,16 @@ private static function filter(array $items, callable $predicate): array
         return array_is_list($items) ? array_values($out) : $out;
     }
 
+    /**
+     * @template T
+     * @param list<T> $items
+     * @return list<T>
+     */
+    private static function take(array $items, int $n): array
+    {
+        return array_slice($items, 0, $n);
+    }
+
     /**
      * @internal
      */

tests/unit/ExpressionTest.php

@@ -126,6 +126,14 @@ public static function evaluateCases(): iterable
                 true,
             ],
             ['myMap:map<int, string>', new Scope(['myMap' => [42 => 'a', 69 => 'b']]), [42 => 'a', 69 => 'b']],
+            [
+                'items:list<string>.take:list<string>(3)',
+                new Scope(['items' => ['a', 'b', 'c', 'd', 'e']]),
+                ['a', 'b', 'c'],
+            ],
+            ['items:list<string>.take:list<string>(3)', new Scope(['items' => ['a', 'b']]), ['a', 'b']],
+            ['items:list<string>.take:list<string>(3)', new Scope(['items' => []]), []],
+            ['items:list<string>.take:list<string>(0)', new Scope(['items' => ['a', 'b', 'c', 'd', 'e']]), []],
         ];
         foreach ($cases as [$expr, $scope, $expected]) {
             $expectedStr = (string)Expr::literal($expected);