diff --git a/src/Psl/Collection/AccessibleCollectionInterface.php b/src/Psl/Collection/AccessibleCollectionInterface.php
index e62df8a..5f131a4 100644
--- a/src/Psl/Collection/AccessibleCollectionInterface.php
+++ b/src/Psl/Collection/AccessibleCollectionInterface.php
@@ -42,7 +42,7 @@ interface AccessibleCollectionInterface extends CollectionInterface, IndexAccess
      * The keys associated with the current `AccessibleCollectionInterface` remain unchanged in the
      * returned `AccessibleCollectionInterface`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback containing the condition to apply to the current
      *                                 `AccessibleCollectionInterface` values
      *
      * @psalm-return AccessibleCollectionInterface<Tk, Tv> - a AccessibleCollectionInterface containing the values after a user-specified condition
@@ -61,7 +61,7 @@ interface AccessibleCollectionInterface extends CollectionInterface, IndexAccess
      * The keys associated with the current `AccessibleCollectionInterface` remain unchanged in the
      * returned `AccessibleCollectionInterface`; the keys will be used in the filtering process only.
      *
-     * @psalm-param (callable(Tk, Tv): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(Tk, Tv): bool) $fn - The callback containing the condition to apply to the current
      *                                     `AccessibleCollectionInterface` keys and values
      *
      * @psalm-return AccessibleCollectionInterface<Tk, Tv> - a `AccessibleCollectionInterface` containing the values after a user-specified
@@ -82,7 +82,7 @@ interface AccessibleCollectionInterface extends CollectionInterface, IndexAccess
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(Tv): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(Tv): Tu) $fn - The callback containing the operation to apply to the current
      *                               `AccessibleCollectionInterface` values
      *
      * @psalm-return AccessibleCollectionInterface<Tk, Tu> - a `AccessibleCollectionInterface` containing key/value pairs after a user-specified
@@ -103,7 +103,7 @@ interface AccessibleCollectionInterface extends CollectionInterface, IndexAccess
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(Tk, Tv): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(Tk, Tv): Tu) $fn - The callback containing the operation to apply to the current
      *                                   `AccessibleCollectionInterface` keys and values
      *
      * @psalm-return AccessibleCollectionInterface<Tk, Tu> - a `AccessibleCollectionInterface` containing the values after a user-specified
@@ -200,7 +200,7 @@ interface AccessibleCollectionInterface extends CollectionInterface, IndexAccess
      * The returned `AccessibleCollectionInterface` will always be a proper subset of the current
      * `AccessibleCollectionInterface`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback that is used to determine the stopping
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback that is used to determine the stopping
      *              condition.
      *
      * @psalm-return AccessibleCollectionInterface<Tk, Tv> - A `AccessibleCollectionInterface` that is a proper subset of the current
@@ -234,7 +234,7 @@ interface AccessibleCollectionInterface extends CollectionInterface, IndexAccess
      * The returned `AccessibleCollectionInterface` will always be a proper subset of the current
      * `AccessibleCollectionInterface`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback used to determine the starting element for the
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback used to determine the starting element for the
      *              returned `AccessibleCollectionInterface`.
      *
      * @psalm-return AccessibleCollectionInterface<Tk, Tv> - A `AccessibleCollectionInterface` that is a proper subset of the current
diff --git a/src/Psl/Collection/CollectionInterface.php b/src/Psl/Collection/CollectionInterface.php
index 0362503..43eeeb8 100644
--- a/src/Psl/Collection/CollectionInterface.php
+++ b/src/Psl/Collection/CollectionInterface.php
@@ -54,7 +54,7 @@ interface CollectionInterface extends Countable, IteratorAggregate, JsonSerializ
      * The keys associated with the current `CollectionInterface` remain unchanged in the
      * returned `CollectionInterface`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback containing the condition to apply to the current
      *                                 `CollectionInterface` values
      *
      * @psalm-return CollectionInterface<Tk, Tv> - a CollectionInterface containing the values after a user-specified condition
@@ -73,7 +73,7 @@ interface CollectionInterface extends Countable, IteratorAggregate, JsonSerializ
      * The keys associated with the current `CollectionInterface` remain unchanged in the
      * returned `CollectionInterface`; the keys will be used in the filtering process only.
      *
-     * @psalm-param (callable(Tk, Tv): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(Tk, Tv): bool) $fn - The callback containing the condition to apply to the current
      *                                     `CollectionInterface` keys and values
      *
      * @psalm-return CollectionInterface<Tk, Tv> - a `CollectionInterface` containing the values after a user-specified
@@ -94,7 +94,7 @@ interface CollectionInterface extends Countable, IteratorAggregate, JsonSerializ
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(Tv): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(Tv): Tu) $fn - The callback containing the operation to apply to the current
      *                               `CollectionInterface` values
      *
      * @psalm-return CollectionInterface<Tk, Tu> - a `CollectionInterface` containing key/value pairs after a user-specified
@@ -115,7 +115,7 @@ interface CollectionInterface extends Countable, IteratorAggregate, JsonSerializ
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(Tk, Tv): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(Tk, Tv): Tu) $fn - The callback containing the operation to apply to the current
      *                                   `CollectionInterface` keys and values
      *
      * @psalm-return CollectionInterface<Tk, Tu> - a `CollectionInterface` containing the values after a user-specified
@@ -168,7 +168,7 @@ interface CollectionInterface extends Countable, IteratorAggregate, JsonSerializ
      * The returned `CollectionInterface` will always be a proper subset of the current
      * `CollectionInterface`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback that is used to determine the stopping
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback that is used to determine the stopping
      *              condition.
      *
      * @psalm-return CollectionInterface<Tk, Tv> - A `CollectionInterface` that is a proper subset of the current
@@ -202,7 +202,7 @@ interface CollectionInterface extends Countable, IteratorAggregate, JsonSerializ
      * The returned `CollectionInterface` will always be a proper subset of the current
      * `CollectionInterface`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback used to determine the starting element for the
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback used to determine the starting element for the
      *              returned `CollectionInterface`.
      *
      * @psalm-return CollectionInterface<Tk, Tv> - A `CollectionInterface` that is a proper subset of the current
diff --git a/src/Psl/Collection/Map.php b/src/Psl/Collection/Map.php
index fadd238..643bd53 100644
--- a/src/Psl/Collection/Map.php
+++ b/src/Psl/Collection/Map.php
@@ -7,6 +7,7 @@ namespace Psl\Collection;
 use Psl;
 use Psl\Arr;
 use Psl\Iter;
+use Psl\Type;
 
 /**
  * @template Tk of array-key
@@ -30,7 +31,7 @@ final class Map implements MapInterface
      */
     public function __construct(iterable $elements)
     {
-        $this->elements = Iter\to_array_with_keys($elements);
+        $this->elements = Type\is_array($elements) ? $elements : iterator_to_array($elements);
     }
 
     /**
@@ -41,18 +42,18 @@ final class Map implements MapInterface
      */
     public function first()
     {
-        return Iter\first($this->elements);
+        return Arr\first($this->elements);
     }
 
     /**
      * Returns the first key in the current collection.
      *
      * @psalm-return Tk|null - The first key in the current collection, or `null` if the
-     *                  current collection is empty
+     *                  current collection is empty.
      */
     public function firstKey()
     {
-        return Iter\first_key($this->elements);
+        return Arr\first_key($this->elements);
     }
 
     /**
@@ -63,18 +64,18 @@ final class Map implements MapInterface
      */
     public function last()
     {
-        return Iter\last($this->elements);
+        return Arr\last($this->elements);
     }
 
     /**
      * Returns the last key in the current collection.
      *
      * @psalm-return Tk|null - The last key in the current collection, or `null` if the
-     *                  current collection is empty
+     *                  current collection is empty.
      */
     public function lastKey()
     {
-        return Iter\last_key($this->elements);
+        return Arr\last_key($this->elements);
     }
 
     /**
@@ -121,7 +122,7 @@ final class Map implements MapInterface
      */
     public function count(): int
     {
-        return Iter\count($this->elements);
+        return Arr\count($this->elements);
     }
 
     /**
@@ -165,7 +166,7 @@ final class Map implements MapInterface
      */
     public function contains($k): bool
     {
-        return Iter\contains_key($this->elements, $k);
+        return Arr\contains_key($this->elements, $k);
     }
 
     /**
@@ -189,7 +190,7 @@ final class Map implements MapInterface
      */
     public function values(): Vector
     {
-        return new Vector(Iter\values($this->elements));
+        return new Vector(Arr\values($this->elements));
     }
 
     /**
@@ -212,7 +213,7 @@ final class Map implements MapInterface
      * The keys associated with the current `Map` remain unchanged in the
      * returned `Map`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback containing the condition to apply to the current
      *                                 `Map` values
      *
      * @psalm-return Map<Tk, Tv> - a Map containing the values after a user-specified condition
@@ -220,7 +221,7 @@ final class Map implements MapInterface
      */
     public function filter(callable $fn): Map
     {
-        return new Map(Iter\filter($this->elements, $fn));
+        return new Map(Arr\filter($this->elements, $fn));
     }
 
     /**
@@ -234,7 +235,7 @@ final class Map implements MapInterface
      * The keys associated with the current `Map` remain unchanged in the
      * returned `Map`; the keys will be used in the filtering process only.
      *
-     * @psalm-param (callable(Tk, Tv): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(Tk, Tv): bool) $fn - The callback containing the condition to apply to the current
      *                                     `Map` keys and values
      *
      * @psalm-return Map<Tk, Tv> - a `Map` containing the values after a user-specified
@@ -243,7 +244,7 @@ final class Map implements MapInterface
      */
     public function filterWithKey(callable $fn): Map
     {
-        return new Map(Iter\filter_with_key($this->elements, $fn));
+        return new Map(Arr\filter_with_key($this->elements, $fn));
     }
 
     /**
@@ -258,7 +259,7 @@ final class Map implements MapInterface
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(Tv): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(Tv): Tu) $fn - The callback containing the operation to apply to the current
      *                               `Map` values
      *
      * @psalm-return   Map<Tk, Tu> - a `Map` containing key/value pairs after a user-specified
@@ -282,7 +283,7 @@ final class Map implements MapInterface
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(Tk, Tv): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(Tk, Tv): Tu) $fn - The callback containing the operation to apply to the current
      *                                   `Map` keys and values
      *
      * @psalm-return   Map<Tk, Tu> - a `Map` containing the values after a user-specified
@@ -351,7 +352,7 @@ final class Map implements MapInterface
      */
     public function take(int $n): Map
     {
-        return new Map(Iter\take($this->elements, $n));
+        return new Map(Arr\take($this->elements, $n));
     }
 
     /**
@@ -362,7 +363,7 @@ final class Map implements MapInterface
      * The returned `Map` will always be a proper subset of the current
      * `Map`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback that is used to determine the stopping
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback that is used to determine the stopping
      *              condition.
      *
      * @psalm-return Map<Tk, Tv> - A `Map` that is a proper subset of the current
@@ -370,7 +371,7 @@ final class Map implements MapInterface
      */
     public function takeWhile(callable $fn): Map
     {
-        return new Map(Iter\take_while($this->elements, $fn));
+        return new Map(Arr\take_while($this->elements, $fn));
     }
 
     /**
@@ -392,7 +393,7 @@ final class Map implements MapInterface
      */
     public function drop(int $n): Map
     {
-        return new Map(Iter\drop($this->elements, $n));
+        return new Map(Arr\drop($this->elements, $n));
     }
 
     /**
@@ -403,7 +404,7 @@ final class Map implements MapInterface
      * The returned `Map` will always be a proper subset of the current
      * `Map`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback used to determine the starting element for the
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback used to determine the starting element for the
      *              returned `Map`.
      *
      * @psalm-return Map<Tk, Tv> - A `Map` that is a proper subset of the current
@@ -411,7 +412,7 @@ final class Map implements MapInterface
      */
     public function dropWhile(callable $fn): Map
     {
-        return new Map(Iter\drop_while($this->elements, $fn));
+        return new Map(Arr\drop_while($this->elements, $fn));
     }
 
     /**
@@ -437,6 +438,6 @@ final class Map implements MapInterface
      */
     public function slice(int $start, int $len): Map
     {
-        return new Map(Iter\slice($this->elements, $start, $len));
+        return new Map(Arr\slice($this->elements, $start, $len));
     }
 }
diff --git a/src/Psl/Collection/MapInterface.php b/src/Psl/Collection/MapInterface.php
index 0f42158..ff941c0 100644
--- a/src/Psl/Collection/MapInterface.php
+++ b/src/Psl/Collection/MapInterface.php
@@ -37,7 +37,7 @@ interface MapInterface extends AccessibleCollectionInterface
      * The keys associated with the current `MapInterface` remain unchanged in the
      * returned `MapInterface`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback containing the condition to apply to the current
      *                                 `MapInterface` values
      *
      * @psalm-return MapInterface<Tk, Tv> - a MapInterface containing the values after a user-specified condition
@@ -56,7 +56,7 @@ interface MapInterface extends AccessibleCollectionInterface
      * The keys associated with the current `MapInterface` remain unchanged in the
      * returned `MapInterface`; the keys will be used in the filtering process only.
      *
-     * @psalm-param (callable(Tk, Tv): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(Tk, Tv): bool) $fn - The callback containing the condition to apply to the current
      *                                     `MapInterface` keys and values
      *
      * @psalm-return MapInterface<Tk, Tv> - a `MapInterface` containing the values after a user-specified
@@ -77,7 +77,7 @@ interface MapInterface extends AccessibleCollectionInterface
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(Tv): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(Tv): Tu) $fn - The callback containing the operation to apply to the current
      *                               `MapInterface` values
      *
      * @psalm-return MapInterface<Tk, Tu> - a `MapInterface` containing key/value pairs after a user-specified
@@ -98,7 +98,7 @@ interface MapInterface extends AccessibleCollectionInterface
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(Tk, Tv): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(Tk, Tv): Tu) $fn - The callback containing the operation to apply to the current
      *                                   `MapInterface` keys and values
      *
      * @psalm-return MapInterface<Tk, Tu> - a `MapInterface` containing the values after a user-specified
@@ -195,7 +195,7 @@ interface MapInterface extends AccessibleCollectionInterface
      * The returned `MapInterface` will always be a proper subset of the current
      * `MapInterface`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback that is used to determine the stopping
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback that is used to determine the stopping
      *              condition.
      *
      * @psalm-return MapInterface<Tk, Tv> - A `MapInterface` that is a proper subset of the current
@@ -229,7 +229,7 @@ interface MapInterface extends AccessibleCollectionInterface
      * The returned `MapInterface` will always be a proper subset of the current
      * `MapInterface`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback used to determine the starting element for the
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback used to determine the starting element for the
      *              returned `MapInterface`.
      *
      * @psalm-return MapInterface<Tk, Tv> - A `MapInterface` that is a proper subset of the current
diff --git a/src/Psl/Collection/MutableAccessibleCollectionInterface.php b/src/Psl/Collection/MutableAccessibleCollectionInterface.php
index da7bfc5..f4a9d41 100644
--- a/src/Psl/Collection/MutableAccessibleCollectionInterface.php
+++ b/src/Psl/Collection/MutableAccessibleCollectionInterface.php
@@ -44,7 +44,7 @@ interface MutableAccessibleCollectionInterface extends AccessibleCollectionInter
      * The keys associated with the current `MutableAccessibleCollectionInterface` remain unchanged in the
      * returned `MutableAccessibleCollectionInterface`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback containing the condition to apply to the current
      *                                 `MutableAccessibleCollectionInterface` values
      *
      * @psalm-return MutableAccessibleCollectionInterface<Tk, Tv> - a Collection containing the values after a user-specified condition
@@ -63,7 +63,7 @@ interface MutableAccessibleCollectionInterface extends AccessibleCollectionInter
      * The keys associated with the current `MutableAccessibleCollectionInterface` remain unchanged in the
      * returned `MutableAccessibleCollectionInterface`; the keys will be used in the filtering process only.
      *
-     * @psalm-param (callable(Tk, Tv): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(Tk, Tv): bool) $fn - The callback containing the condition to apply to the current
      *                                     `MutableAccessibleCollectionInterface` keys and values
      *
      * @psalm-return MutableAccessibleCollectionInterface<Tk, Tv> - a `MutableAccessibleCollectionInterface` containing the values after a user-specified
@@ -84,7 +84,7 @@ interface MutableAccessibleCollectionInterface extends AccessibleCollectionInter
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(Tv): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(Tv): Tu) $fn - The callback containing the operation to apply to the current
      *                               `MutableAccessibleCollectionInterface` values
      *
      * @psalm-return MutableAccessibleCollectionInterface<Tk, Tu> - a `MutableAccessibleCollectionInterface` containing key/value pairs after a user-specified
@@ -105,7 +105,7 @@ interface MutableAccessibleCollectionInterface extends AccessibleCollectionInter
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(Tk, Tv): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(Tk, Tv): Tu) $fn - The callback containing the operation to apply to the current
      *                                   `MutableAccessibleCollectionInterface` keys and values
      *
      * @psalm-return MutableAccessibleCollectionInterface<Tk, Tu> - a `MutableAccessibleCollectionInterface` containing the values after a user-specified
@@ -215,7 +215,7 @@ interface MutableAccessibleCollectionInterface extends AccessibleCollectionInter
      * The returned `MutableAccessibleCollectionInterface` will always be a proper subset of the current
      * `MutableAccessibleCollectionInterface`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback that is used to determine the stopping
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback that is used to determine the stopping
      *              condition.
      *
      * @psalm-return MutableAccessibleCollectionInterface<Tk, Tv> - A `MutableAccessibleCollectionInterface` that is a proper subset of the current
@@ -249,7 +249,7 @@ interface MutableAccessibleCollectionInterface extends AccessibleCollectionInter
      * The returned `MutableAccessibleCollectionInterface` will always be a proper subset of the current
      * `MutableAccessibleCollectionInterface`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback used to determine the starting element for the
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback used to determine the starting element for the
      *              returned `MutableAccessibleCollectionInterface`.
      *
      * @psalm-return MutableAccessibleCollectionInterface<Tk, Tv> - A `MutableAccessibleCollectionInterface` that is a proper subset of the current
diff --git a/src/Psl/Collection/MutableCollectionInterface.php b/src/Psl/Collection/MutableCollectionInterface.php
index f11e30c..80060bb 100644
--- a/src/Psl/Collection/MutableCollectionInterface.php
+++ b/src/Psl/Collection/MutableCollectionInterface.php
@@ -29,7 +29,7 @@ interface MutableCollectionInterface extends CollectionInterface
      * The keys associated with the current `MutableCollectionInterface` remain unchanged in the
      * returned `MutableCollectionInterface`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback containing the condition to apply to the current
      *                                 `MutableCollectionInterface` values
      *
      * @psalm-return MutableCollectionInterface<Tk, Tv> - a Collection containing the values after a user-specified condition
@@ -48,7 +48,7 @@ interface MutableCollectionInterface extends CollectionInterface
      * The keys associated with the current `MutableCollectionInterface` remain unchanged in the
      * returned `MutableCollectionInterface`; the keys will be used in the filtering process only.
      *
-     * @psalm-param (callable(Tk, Tv): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(Tk, Tv): bool) $fn - The callback containing the condition to apply to the current
      *                                     `MutableCollectionInterface` keys and values
      *
      * @psalm-return MutableCollectionInterface<Tk, Tv> - a `MutableCollectionInterface` containing the values after a user-specified
@@ -69,7 +69,7 @@ interface MutableCollectionInterface extends CollectionInterface
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(Tv): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(Tv): Tu) $fn - The callback containing the operation to apply to the current
      *                               `MutableCollectionInterface` values
      *
      * @psalm-return MutableCollectionInterface<Tk, Tu> - a `MutableCollectionInterface` containing key/value pairs after a user-specified
@@ -90,7 +90,7 @@ interface MutableCollectionInterface extends CollectionInterface
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(Tk, Tv): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(Tk, Tv): Tu) $fn - The callback containing the operation to apply to the current
      *                                   `MutableCollectionInterface` keys and values
      *
      * @psalm-return MutableCollectionInterface<Tk, Tu> - a `MutableCollectionInterface` containing the values after a user-specified
@@ -143,7 +143,7 @@ interface MutableCollectionInterface extends CollectionInterface
      * The returned `MutableCollectionInterface` will always be a proper subset of the current
      * `MutableCollectionInterface`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback that is used to determine the stopping
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback that is used to determine the stopping
      *              condition.
      *
      * @psalm-return MutableCollectionInterface<Tk, Tv> - A `MutableCollectionInterface` that is a proper subset of the current
@@ -177,7 +177,7 @@ interface MutableCollectionInterface extends CollectionInterface
      * The returned `MutableCollectionInterface` will always be a proper subset of the current
      * `MutableCollectionInterface`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback used to determine the starting element for the
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback used to determine the starting element for the
      *              returned `MutableCollectionInterface`.
      *
      * @psalm-return MutableCollectionInterface<Tk, Tv> - A `MutableCollectionInterface` that is a proper subset of the current
diff --git a/src/Psl/Collection/MutableMap.php b/src/Psl/Collection/MutableMap.php
index f7c26a8..e6f27d0 100644
--- a/src/Psl/Collection/MutableMap.php
+++ b/src/Psl/Collection/MutableMap.php
@@ -39,7 +39,7 @@ final class MutableMap implements MutableMapInterface
      */
     public function first()
     {
-        return Iter\first($this->elements);
+        return Arr\first($this->elements);
     }
 
     /**
@@ -50,7 +50,7 @@ final class MutableMap implements MutableMapInterface
      */
     public function firstKey()
     {
-        return Iter\first_key($this->elements);
+        return Arr\first_key($this->elements);
     }
 
     /**
@@ -61,7 +61,7 @@ final class MutableMap implements MutableMapInterface
      */
     public function last()
     {
-        return Iter\last($this->elements);
+        return Arr\last($this->elements);
     }
 
     /**
@@ -72,7 +72,7 @@ final class MutableMap implements MutableMapInterface
      */
     public function lastKey()
     {
-        return Iter\last_key($this->elements);
+        return Arr\last_key($this->elements);
     }
 
     /**
@@ -119,7 +119,7 @@ final class MutableMap implements MutableMapInterface
      */
     public function count(): int
     {
-        return Iter\count($this->elements);
+        return Arr\count($this->elements);
     }
 
     /**
@@ -163,7 +163,7 @@ final class MutableMap implements MutableMapInterface
      */
     public function contains($k): bool
     {
-        return Iter\contains_key($this->elements, $k);
+        return Arr\contains_key($this->elements, $k);
     }
 
     /**
@@ -186,7 +186,7 @@ final class MutableMap implements MutableMapInterface
      */
     public function values(): MutableVector
     {
-        return new MutableVector(Iter\values($this->elements));
+        return new MutableVector(Arr\values($this->elements));
     }
 
     /**
@@ -196,7 +196,7 @@ final class MutableMap implements MutableMapInterface
      */
     public function keys(): MutableVector
     {
-        return new MutableVector(Iter\keys($this->elements));
+        return new MutableVector(Arr\keys($this->elements));
     }
 
     /**
@@ -209,7 +209,7 @@ final class MutableMap implements MutableMapInterface
      * The keys associated with the current `MutableMap` remain unchanged in the
      * returned `MutableMap`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback containing the condition to apply to the current
      *                                 `MutableMap` values
      *
      * @psalm-return MutableMap<Tk, Tv> - a MutableMap containing the values after a user-specified condition
@@ -217,7 +217,7 @@ final class MutableMap implements MutableMapInterface
      */
     public function filter(callable $fn): MutableMap
     {
-        return new MutableMap(Iter\filter($this->elements, $fn));
+        return new MutableMap(Arr\filter($this->elements, $fn));
     }
 
     /**
@@ -231,7 +231,7 @@ final class MutableMap implements MutableMapInterface
      * The keys associated with the current `MutableMap` remain unchanged in the
      * returned `MutableMap`; the keys will be used in the filtering process only.
      *
-     * @psalm-param (callable(Tk, Tv): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(Tk, Tv): bool) $fn - The callback containing the condition to apply to the current
      *                                     `MutableMap` keys and values
      *
      * @psalm-return MutableMap<Tk, Tv> - a `MutableMap` containing the values after a user-specified
@@ -240,7 +240,7 @@ final class MutableMap implements MutableMapInterface
      */
     public function filterWithKey(callable $fn): MutableMap
     {
-        return new MutableMap(Iter\filter_with_key($this->elements, $fn));
+        return new MutableMap(Arr\filter_with_key($this->elements, $fn));
     }
 
     /**
@@ -255,7 +255,7 @@ final class MutableMap implements MutableMapInterface
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(Tv): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(Tv): Tu) $fn - The callback containing the operation to apply to the current
      *                               `MutableMap` values
      *
      * @psalm-return   MutableMap<Tk, Tu> - a `MutableMap` containing key/value pairs after a user-specified
@@ -279,7 +279,7 @@ final class MutableMap implements MutableMapInterface
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(Tk, Tv): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(Tk, Tv): Tu) $fn - The callback containing the operation to apply to the current
      *                                   `MutableMap` keys and values
      *
      * @psalm-return   MutableMap<Tk, Tu> - a `MutableMap` containing the values after a user-specified
@@ -348,7 +348,7 @@ final class MutableMap implements MutableMapInterface
      */
     public function take(int $n): MutableMap
     {
-        return new MutableMap(Iter\take($this->elements, $n));
+        return new MutableMap(Arr\take($this->elements, $n));
     }
 
     /**
@@ -359,7 +359,7 @@ final class MutableMap implements MutableMapInterface
      * The returned `MutableMap` will always be a proper subset of the current
      * `MutableMap`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback that is used to determine the stopping
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback that is used to determine the stopping
      *              condition.
      *
      * @psalm-return MutableMap<Tk, Tv> - A `MutableMap` that is a proper subset of the current
@@ -367,7 +367,7 @@ final class MutableMap implements MutableMapInterface
      */
     public function takeWhile(callable $fn): MutableMap
     {
-        return new MutableMap(Iter\take_while($this->elements, $fn));
+        return new MutableMap(Arr\take_while($this->elements, $fn));
     }
 
     /**
@@ -390,7 +390,7 @@ final class MutableMap implements MutableMapInterface
      */
     public function drop(int $n): MutableMap
     {
-        return new MutableMap(Iter\drop($this->elements, $n));
+        return new MutableMap(Arr\drop($this->elements, $n));
     }
 
     /**
@@ -401,7 +401,7 @@ final class MutableMap implements MutableMapInterface
      * The returned `MutableMap` will always be a proper subset of the current
      * `MutableMap`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback used to determine the starting element for the
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback used to determine the starting element for the
      *              returned `MutableMap`.
      *
      * @psalm-return MutableMap<Tk, Tv> - A `MutableMap` that is a proper subset of the current
@@ -409,7 +409,7 @@ final class MutableMap implements MutableMapInterface
      */
     public function dropWhile(callable $fn): MutableMap
     {
-        return new MutableMap(Iter\drop_while($this->elements, $fn));
+        return new MutableMap(Arr\drop_while($this->elements, $fn));
     }
 
     /**
@@ -435,7 +435,7 @@ final class MutableMap implements MutableMapInterface
      */
     public function slice(int $start, int $len): MutableMap
     {
-        return new MutableMap(Iter\slice($this->elements, $start, $len));
+        return new MutableMap(Arr\slice($this->elements, $start, $len));
     }
 
     /**
diff --git a/src/Psl/Collection/MutableMapInterface.php b/src/Psl/Collection/MutableMapInterface.php
index 27bb66d..e99d00d 100644
--- a/src/Psl/Collection/MutableMapInterface.php
+++ b/src/Psl/Collection/MutableMapInterface.php
@@ -38,7 +38,7 @@ interface MutableMapInterface extends MapInterface, MutableAccessibleCollectionI
      * The keys associated with the current `MutableMapInterface` remain unchanged in the
      * returned `MutableMapInterface`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback containing the condition to apply to the current
      *                                 `MutableMapInterface` values
      *
      * @psalm-return MutableMapInterface<Tk, Tv> - a MutableMapInterface containing the values after a user-specified condition
@@ -57,7 +57,7 @@ interface MutableMapInterface extends MapInterface, MutableAccessibleCollectionI
      * The keys associated with the current `MutableMapInterface` remain unchanged in the
      * returned `MutableMapInterface`; the keys will be used in the filtering process only.
      *
-     * @psalm-param (callable(Tk, Tv): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(Tk, Tv): bool) $fn - The callback containing the condition to apply to the current
      *                                     `MutableMapInterface` keys and values
      *
      * @psalm-return MutableMapInterface<Tk, Tv> - a `MutableMapInterface` containing the values after a user-specified
@@ -78,7 +78,7 @@ interface MutableMapInterface extends MapInterface, MutableAccessibleCollectionI
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(Tv): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(Tv): Tu) $fn - The callback containing the operation to apply to the current
      *                               `MutableMapInterface` values
      *
      * @psalm-return MutableMapInterface<Tk, Tu> - a `MutableMapInterface` containing key/value pairs after a user-specified
@@ -99,7 +99,7 @@ interface MutableMapInterface extends MapInterface, MutableAccessibleCollectionI
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(Tk, Tv): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(Tk, Tv): Tu) $fn - The callback containing the operation to apply to the current
      *                                   `MutableMapInterface` keys and values
      *
      * @psalm-return MutableMapInterface<Tk, Tu> - a `MutableMapInterface` containing the values after a user-specified
@@ -196,7 +196,7 @@ interface MutableMapInterface extends MapInterface, MutableAccessibleCollectionI
      * The returned `MutableMapInterface` will always be a proper subset of the current
      * `MutableMapInterface`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback that is used to determine the stopping
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback that is used to determine the stopping
      *              condition.
      *
      * @psalm-return MutableMapInterface<Tk, Tv> - A `MutableMapInterface` that is a proper subset of the current
@@ -230,7 +230,7 @@ interface MutableMapInterface extends MapInterface, MutableAccessibleCollectionI
      * The returned `MutableMapInterface` will always be a proper subset of the current
      * `MutableMapInterface`.
      *
-     * @psalm-param (callable(Tv): bool) $fn - The callback used to determine the starting element for the
+     * @psalm-param (pure-callable(Tv): bool) $fn - The callback used to determine the starting element for the
      *              returned `MutableMapInterface`.
      *
      * @psalm-return MutableMapInterface<Tk, Tv> - A `MutableMapInterface` that is a proper subset of the current
diff --git a/src/Psl/Collection/MutableVector.php b/src/Psl/Collection/MutableVector.php
index add8f2f..fdfb4f1 100644
--- a/src/Psl/Collection/MutableVector.php
+++ b/src/Psl/Collection/MutableVector.php
@@ -40,7 +40,7 @@ final class MutableVector implements MutableVectorInterface
      */
     public function first()
     {
-        return Iter\first($this->elements);
+        return Arr\first($this->elements);
     }
 
     /**
@@ -51,7 +51,7 @@ final class MutableVector implements MutableVectorInterface
      */
     public function last()
     {
-        return Iter\last($this->elements);
+        return Arr\last($this->elements);
     }
 
     /**
@@ -77,7 +77,7 @@ final class MutableVector implements MutableVectorInterface
      */
     public function count(): int
     {
-        return Iter\count($this->elements);
+        return Arr\count($this->elements);
     }
 
     /**
@@ -121,7 +121,7 @@ final class MutableVector implements MutableVectorInterface
      */
     public function contains($k): bool
     {
-        return Iter\contains_key($this->elements, $k);
+        return Arr\contains_key($this->elements, $k);
     }
 
     /**
@@ -335,7 +335,7 @@ final class MutableVector implements MutableVectorInterface
      * The keys associated with the current `MutableVector` remain unchanged in the
      * returned `MutableVector`.
      *
-     * @psalm-param (callable(T): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(T): bool) $fn - The callback containing the condition to apply to the current
      *                                 `MutableVector` values
      *
      * @psalm-return MutableVector<T> - a MutableVector containing the values after a user-specified condition
@@ -343,7 +343,7 @@ final class MutableVector implements MutableVectorInterface
      */
     public function filter(callable $fn): MutableVector
     {
-        return new MutableVector(Iter\filter($this->elements, $fn));
+        return new MutableVector(Arr\filter($this->elements, $fn));
     }
 
     /**
@@ -357,7 +357,7 @@ final class MutableVector implements MutableVectorInterface
      * The keys associated with the current `MutableVector` remain unchanged in the
      * returned `MutableVector`; the keys will be used in the filtering process only.
      *
-     * @psalm-param (callable(int, T): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(int, T): bool) $fn - The callback containing the condition to apply to the current
      *                                     `MutableVector` keys and values
      *
      * @psalm-return MutableVector<T> - a `MutableVector` containing the values after a user-specified
@@ -366,7 +366,7 @@ final class MutableVector implements MutableVectorInterface
      */
     public function filterWithKey(callable $fn): MutableVector
     {
-        return new MutableVector(Iter\filter_with_key($this->elements, $fn));
+        return new MutableVector(Arr\filter_with_key($this->elements, $fn));
     }
 
     /**
@@ -381,7 +381,7 @@ final class MutableVector implements MutableVectorInterface
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(T): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(T): Tu) $fn - The callback containing the operation to apply to the current
      *                               `MutableVector` values
      *
      * @psalm-return   MutableVector<Tu> - a `MutableVector` containing key/value pairs after a user-specified
@@ -405,7 +405,7 @@ final class MutableVector implements MutableVectorInterface
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(int, T): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(int, T): Tu) $fn - The callback containing the operation to apply to the current
      *                                   `MutableVector` keys and values
      *
      * @psalm-return   MutableVector<Tu> - a `MutableVector` containing the values after a user-specified
@@ -470,7 +470,7 @@ final class MutableVector implements MutableVectorInterface
      */
     public function take(int $n): MutableVector
     {
-        return new MutableVector(Iter\take($this->elements, $n));
+        return new MutableVector(Arr\take($this->elements, $n));
     }
 
     /**
@@ -481,7 +481,7 @@ final class MutableVector implements MutableVectorInterface
      * The returned `MutableVector` will always be a proper subset of the current
      * `MutableVector`.
      *
-     * @psalm-param (callable(T): bool) $fn - The callback that is used to determine the stopping
+     * @psalm-param (pure-callable(T): bool) $fn - The callback that is used to determine the stopping
      *              condition.
      *
      * @psalm-return MutableVector<T> - A `MutableVector` that is a proper subset of the current
@@ -489,7 +489,7 @@ final class MutableVector implements MutableVectorInterface
      */
     public function takeWhile(callable $fn): MutableVector
     {
-        return new MutableVector(Iter\take_while($this->elements, $fn));
+        return new MutableVector(Arr\take_while($this->elements, $fn));
     }
 
     /**
@@ -512,7 +512,7 @@ final class MutableVector implements MutableVectorInterface
      */
     public function drop(int $n): MutableVector
     {
-        return new MutableVector(Iter\drop($this->elements, $n));
+        return new MutableVector(Arr\drop($this->elements, $n));
     }
 
     /**
@@ -523,7 +523,7 @@ final class MutableVector implements MutableVectorInterface
      * The returned `MutableVector` will always be a proper subset of the current
      * `MutableVector`.
      *
-     * @psalm-param (callable(T): bool) $fn - The callback used to determine the starting element for the
+     * @psalm-param (pure-callable(T): bool) $fn - The callback used to determine the starting element for the
      *              returned `MutableVector`.
      *
      * @psalm-return MutableVector<T> - A `MutableVector` that is a proper subset of the current
@@ -531,7 +531,7 @@ final class MutableVector implements MutableVectorInterface
      */
     public function dropWhile(callable $fn): MutableVector
     {
-        return new MutableVector(Iter\drop_while($this->elements, $fn));
+        return new MutableVector(Arr\drop_while($this->elements, $fn));
     }
 
     /**
@@ -557,6 +557,6 @@ final class MutableVector implements MutableVectorInterface
      */
     public function slice(int $start, int $len): MutableVector
     {
-        return new MutableVector(Iter\slice($this->elements, $start, $len));
+        return new MutableVector(Arr\slice($this->elements, $start, $len));
     }
 }
diff --git a/src/Psl/Collection/MutableVectorInterface.php b/src/Psl/Collection/MutableVectorInterface.php
index fc0631a..f45af45 100644
--- a/src/Psl/Collection/MutableVectorInterface.php
+++ b/src/Psl/Collection/MutableVectorInterface.php
@@ -44,7 +44,7 @@ interface MutableVectorInterface extends VectorInterface, MutableAccessibleColle
      * The keys associated with the current `MutableVectorInterface` remain unchanged in the
      * returned `MutableVectorInterface`.
      *
-     * @psalm-param (callable(T): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(T): bool) $fn - The callback containing the condition to apply to the current
      *                                 `MutableVectorInterface` values
      *
      * @psalm-return MutableVectorInterface<T> - a MutableVectorInterface containing the values after a user-specified condition
@@ -63,7 +63,7 @@ interface MutableVectorInterface extends VectorInterface, MutableAccessibleColle
      * The keys associated with the current `MutableVectorInterface` remain unchanged in the
      * returned `MutableVectorInterface`; the keys will be used in the filtering process only.
      *
-     * @psalm-param (callable(int, T): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(int, T): bool) $fn - The callback containing the condition to apply to the current
      *                                     `MutableVectorInterface` keys and values
      *
      * @psalm-return MutableVectorInterface<T> - a `MutableVectorInterface` containing the values after a user-specified
@@ -84,7 +84,7 @@ interface MutableVectorInterface extends VectorInterface, MutableAccessibleColle
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(T): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(T): Tu) $fn - The callback containing the operation to apply to the current
      *                               `MutableVectorInterface` values
      *
      * @psalm-return   MutableVectorInterface<Tu> - a `MutableVectorInterface` containing key/value pairs after a user-specified
@@ -105,7 +105,7 @@ interface MutableVectorInterface extends VectorInterface, MutableAccessibleColle
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(int, T): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(int, T): Tu) $fn - The callback containing the operation to apply to the current
      *                                   `MutableVectorInterface` keys and values
      *
      * @psalm-return   MutableVectorInterface<Tu> - a `MutableVectorInterface` containing the values after a user-specified
@@ -202,7 +202,7 @@ interface MutableVectorInterface extends VectorInterface, MutableAccessibleColle
      * The returned `MutableVectorInterface` will always be a proper subset of the current
      * `MutableVectorInterface`.
      *
-     * @psalm-param (callable(T): bool) $fn - The callback that is used to determine the stopping
+     * @psalm-param (pure-callable(T): bool) $fn - The callback that is used to determine the stopping
      *              condition.
      *
      * @psalm-return MutableVectorInterface<T> - A `MutableVectorInterface` that is a proper subset of the current
@@ -236,7 +236,7 @@ interface MutableVectorInterface extends VectorInterface, MutableAccessibleColle
      * The returned `MutableVectorInterface` will always be a proper subset of the current
      * `MutableVectorInterface`.
      *
-     * @psalm-param (callable(T): bool) $fn - The callback used to determine the starting element for the
+     * @psalm-param (pure-callable(T): bool) $fn - The callback used to determine the starting element for the
      *              returned `MutableVectorInterface`.
      *
      * @psalm-return MutableVectorInterface<T> - A `MutableVectorInterface` that is a proper subset of the current
diff --git a/src/Psl/Collection/Vector.php b/src/Psl/Collection/Vector.php
index 57264ab..bfe65cc 100644
--- a/src/Psl/Collection/Vector.php
+++ b/src/Psl/Collection/Vector.php
@@ -42,7 +42,7 @@ final class Vector implements VectorInterface
      */
     public function first()
     {
-        return Iter\first($this->elements);
+        return Arr\first($this->elements);
     }
 
     /**
@@ -53,7 +53,7 @@ final class Vector implements VectorInterface
      */
     public function last()
     {
-        return Iter\last($this->elements);
+        return Arr\last($this->elements);
     }
 
     /**
@@ -79,7 +79,7 @@ final class Vector implements VectorInterface
      */
     public function count(): int
     {
-        return Iter\count($this->elements);
+        return Arr\count($this->elements);
     }
 
     /**
@@ -124,7 +124,7 @@ final class Vector implements VectorInterface
      */
     public function contains($k): bool
     {
-        return Iter\contains_key($this->elements, $k);
+        return Arr\contains_key($this->elements, $k);
     }
 
     /**
@@ -219,7 +219,7 @@ final class Vector implements VectorInterface
      * The keys associated with the current `Vector` remain unchanged in the
      * returned `Vector`.
      *
-     * @psalm-param (callable(T): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(T): bool) $fn - The callback containing the condition to apply to the current
      *                                 `Vector` values
      *
      * @psalm-return Vector<T> - a Vector containing the values after a user-specified condition
@@ -227,7 +227,7 @@ final class Vector implements VectorInterface
      */
     public function filter(callable $fn): Vector
     {
-        return new Vector(Iter\filter($this->elements, $fn));
+        return new Vector(Arr\filter($this->elements, $fn));
     }
 
     /**
@@ -241,7 +241,7 @@ final class Vector implements VectorInterface
      * The keys associated with the current `Vector` remain unchanged in the
      * returned `Vector`; the keys will be used in the filtering process only.
      *
-     * @psalm-param (callable(int, T): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(int, T): bool) $fn - The callback containing the condition to apply to the current
      *                                     `Vector` keys and values
      *
      * @psalm-return Vector<T> - a `Vector` containing the values after a user-specified
@@ -250,7 +250,7 @@ final class Vector implements VectorInterface
      */
     public function filterWithKey(callable $fn): Vector
     {
-        return new Vector(Iter\filter_with_key($this->elements, $fn));
+        return new Vector(Arr\filter_with_key($this->elements, $fn));
     }
 
     /**
@@ -265,7 +265,7 @@ final class Vector implements VectorInterface
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(T): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(T): Tu) $fn - The callback containing the operation to apply to the current
      *                               `Vector` values
      *
      * @psalm-return   Vector<Tu> - a `Vector` containing key/value pairs after a user-specified
@@ -289,7 +289,7 @@ final class Vector implements VectorInterface
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(int, T): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(int, T): Tu) $fn - The callback containing the operation to apply to the current
      *                                   `Vector` keys and values
      *
      * @psalm-return   Vector<Tu> - a `Vector` containing the values after a user-specified
@@ -354,7 +354,7 @@ final class Vector implements VectorInterface
      */
     public function take(int $n): Vector
     {
-        return new Vector(Iter\take($this->elements, $n));
+        return new Vector(Arr\take($this->elements, $n));
     }
 
     /**
@@ -365,7 +365,7 @@ final class Vector implements VectorInterface
      * The returned `Vector` will always be a proper subset of the current
      * `Vector`.
      *
-     * @psalm-param (callable(T): bool) $fn - The callback that is used to determine the stopping
+     * @psalm-param (pure-callable(T): bool) $fn - The callback that is used to determine the stopping
      *              condition.
      *
      * @psalm-return Vector<T> - A `Vector` that is a proper subset of the current
@@ -373,7 +373,7 @@ final class Vector implements VectorInterface
      */
     public function takeWhile(callable $fn): Vector
     {
-        return new Vector(Iter\take_while($this->elements, $fn));
+        return new Vector(Arr\take_while($this->elements, $fn));
     }
 
     /**
@@ -396,7 +396,7 @@ final class Vector implements VectorInterface
      */
     public function drop(int $n): Vector
     {
-        return new Vector(Iter\drop($this->elements, $n));
+        return new Vector(Arr\drop($this->elements, $n));
     }
 
     /**
@@ -407,7 +407,7 @@ final class Vector implements VectorInterface
      * The returned `Vector` will always be a proper subset of the current
      * `Vector`.
      *
-     * @psalm-param (callable(T): bool) $fn - The callback used to determine the starting element for the
+     * @psalm-param (pure-callable(T): bool) $fn - The callback used to determine the starting element for the
      *              returned `Vector`.
      *
      * @psalm-return Vector<T> - A `Vector` that is a proper subset of the current
@@ -415,7 +415,7 @@ final class Vector implements VectorInterface
      */
     public function dropWhile(callable $fn): Vector
     {
-        return new Vector(Iter\drop_while($this->elements, $fn));
+        return new Vector(Arr\drop_while($this->elements, $fn));
     }
 
     /**
@@ -441,6 +441,6 @@ final class Vector implements VectorInterface
      */
     public function slice(int $start, int $len): Vector
     {
-        return new Vector(Iter\slice($this->elements, $start, $len));
+        return new Vector(Arr\slice($this->elements, $start, $len));
     }
 }
diff --git a/src/Psl/Collection/VectorInterface.php b/src/Psl/Collection/VectorInterface.php
index 2474ff8..b1b8bba 100644
--- a/src/Psl/Collection/VectorInterface.php
+++ b/src/Psl/Collection/VectorInterface.php
@@ -68,7 +68,7 @@ interface VectorInterface extends AccessibleCollectionInterface
      * The keys associated with the current `VectorInterface` remain unchanged in the
      * returned `VectorInterface`.
      *
-     * @psalm-param (callable(T): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(T): bool) $fn - The callback containing the condition to apply to the current
      *                                 `VectorInterface` values
      *
      * @psalm-return VectorInterface<T> - a VectorInterface containing the values after a user-specified condition
@@ -87,7 +87,7 @@ interface VectorInterface extends AccessibleCollectionInterface
      * The keys associated with the current `VectorInterface` remain unchanged in the
      * returned `VectorInterface`; the keys will be used in the filtering process only.
      *
-     * @psalm-param (callable(int, T): bool) $fn - The callback containing the condition to apply to the current
+     * @psalm-param (pure-callable(int, T): bool) $fn - The callback containing the condition to apply to the current
      *                                     `VectorInterface` keys and values
      *
      * @psalm-return VectorInterface<T> - a `VectorInterface` containing the values after a user-specified
@@ -108,7 +108,7 @@ interface VectorInterface extends AccessibleCollectionInterface
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(T): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(T): Tu) $fn - The callback containing the operation to apply to the current
      *                               `VectorInterface` values
      *
      * @psalm-return   VectorInterface<Tu> - a `VectorInterface` containing key/value pairs after a user-specified
@@ -129,7 +129,7 @@ interface VectorInterface extends AccessibleCollectionInterface
      *
      * @psalm-template Tu
      *
-     * @psalm-param (callable(int, T): Tu) $fn - The callback containing the operation to apply to the current
+     * @psalm-param (pure-callable(int, T): Tu) $fn - The callback containing the operation to apply to the current
      *                                   `VectorInterface` keys and values
      *
      * @psalm-return   VectorInterface<Tu> - a `VectorInterface` containing the values after a user-specified
@@ -226,7 +226,7 @@ interface VectorInterface extends AccessibleCollectionInterface
      * The returned `VectorInterface` will always be a proper subset of the current
      * `VectorInterface`.
      *
-     * @psalm-param (callable(T): bool) $fn - The callback that is used to determine the stopping
+     * @psalm-param (pure-callable(T): bool) $fn - The callback that is used to determine the stopping
      *              condition.
      *
      * @psalm-return VectorInterface<T> - A `VectorInterface` that is a proper subset of the current
@@ -260,7 +260,7 @@ interface VectorInterface extends AccessibleCollectionInterface
      * The returned `VectorInterface` will always be a proper subset of the current
      * `VectorInterface`.
      *
-     * @psalm-param (callable(T): bool) $fn - The callback used to determine the starting element for the
+     * @psalm-param (pure-callable(T): bool) $fn - The callback used to determine the starting element for the
      *              returned `VectorInterface`.
      *
      * @psalm-return VectorInterface<T> - A `VectorInterface` that is a proper subset of the current