Add map() function

README.md

@@ -100,13 +100,14 @@ The target can be any expression. It will be passed as the first argument to the
 
 #### Built-In Functions
 
-| Function   | Description                                                 | Example                                          |
-|------------|-------------------------------------------------------------|--------------------------------------------------|
-| `count`    | Returns the number of elements in a list                    | `foo:list<string>.count:int()`                   |
-| `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)`          |
+| Function   | Description                                                            | Example                                          |
+|------------|------------------------------------------------------------------------|--------------------------------------------------|
+| `count`    | Returns the number of elements in a list                               | `foo:list<string>.count:int()`                   |
+| `contains` | Returns whether a list contains a value                                | `foo:list<string>.contains:bool("bar")`          |
+| `map`      | Returns a new list with the results of applying a [function](#lambdas) | `foo:list<int>.map:list<int>(\|i\| i:int - 2)`   |
+| `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

@@ -43,6 +43,7 @@ public function __construct(private readonly array $vars = [], array $funcs = []
             'contains' => self::contains(...),
             'count' => self::count(...),
             'filter' => self::filter(...),
+            'map' => self::map(...),
             'some' => self::some(...),
             'substr' => substr(...),
             'take' => self::take(...),
@@ -69,6 +70,19 @@ public function __construct(private readonly array $vars = [], array $funcs = []
         }
     }
 
+    /**
+     * @template K of array-key
+     * @template From
+     * @template To
+     * @param array<K, From> $items
+     * @param callable(From): To $f
+     * @return array<K, To>
+     */
+    private static function map(array $items, callable $f): array
+    {
+        return array_map($f, $items);
+    }
+
     /**
      * @template T
      * @param array<array-key, T> $haystack

tests/unit/ExpressionTest.php

@@ -135,6 +135,12 @@ public static function evaluateCases(): iterable
             ['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']]), []],
             ['-myval:int', new Scope(['myval' => 42]), -42],
+            [
+                'names:list<string>.map:list<bool>(|name| name:string === "bar")',
+                new Scope(['names' => ['foo', 'bar', 'baz']]),
+                [false, true, false],
+            ],
+            ['ints:list<int>.map:list<int>(|i| i:int -2)', new Scope(['ints' => []]), []],
         ];
         foreach ($cases as [$expr, $scope, $expected]) {
             $expectedStr = (string)Expr::literal($expected);