From b33d6b2003efef272e4c6741e1d26e960a92622d Mon Sep 17 00:00:00 2001
From: Saif Eddin Gmati <29315886+azjezz@users.noreply.github.com>
Date: Fri, 19 Feb 2021 21:04:54 +0100
Subject: [PATCH] [Vec] add filter and map functions (#136)

---
 src/Psl/Dict/filter.php             |  8 ++---
 src/Psl/Dict/filter_keys.php        | 10 +++---
 src/Psl/Dict/filter_nulls.php       | 32 ++++++++++++++++++
 src/Psl/Dict/filter_with_key.php    |  8 ++---
 src/Psl/Internal/Loader.php         |  6 ++++
 src/Psl/Vec/filter.php              | 42 ++++++++++++++++++++++++
 src/Psl/Vec/filter_keys.php         | 43 ++++++++++++++++++++++++
 src/Psl/Vec/filter_with_key.php     | 51 +++++++++++++++++++++++++++++
 src/Psl/Vec/map.php                 | 35 ++++++++++++++++++++
 src/Psl/Vec/map_with_key.php        | 35 ++++++++++++++++++++
 tests/Psl/Dict/FilterNullsTest.php  | 35 ++++++++++++++++++++
 tests/Psl/Vec/ChunkTest.php         | 33 +++++++++++++++++++
 tests/Psl/Vec/FilterKeysTest.php    | 31 ++++++++++++++++++
 tests/Psl/Vec/FilterTest.php        | 30 +++++++++++++++++
 tests/Psl/Vec/FilterWithKeyTest.php | 34 +++++++++++++++++++
 tests/Psl/Vec/MapTest.php           | 29 ++++++++++++++++
 tests/Psl/Vec/MapWithKeyTest.php    | 30 +++++++++++++++++
 tests/Psl/Vec/ZipTest.php           | 40 ++++++++++++++++++++++
 18 files changed, 519 insertions(+), 13 deletions(-)
 create mode 100644 src/Psl/Dict/filter_nulls.php
 create mode 100644 src/Psl/Vec/filter.php
 create mode 100644 src/Psl/Vec/filter_keys.php
 create mode 100644 src/Psl/Vec/filter_with_key.php
 create mode 100644 src/Psl/Vec/map.php
 create mode 100644 src/Psl/Vec/map_with_key.php
 create mode 100644 tests/Psl/Dict/FilterNullsTest.php
 create mode 100644 tests/Psl/Vec/ChunkTest.php
 create mode 100644 tests/Psl/Vec/FilterKeysTest.php
 create mode 100644 tests/Psl/Vec/FilterTest.php
 create mode 100644 tests/Psl/Vec/FilterWithKeyTest.php
 create mode 100644 tests/Psl/Vec/MapTest.php
 create mode 100644 tests/Psl/Vec/MapWithKeyTest.php
 create mode 100644 tests/Psl/Vec/ZipTest.php

diff --git a/src/Psl/Dict/filter.php b/src/Psl/Dict/filter.php
index fd5273b..b3f25c2 100644
--- a/src/Psl/Dict/filter.php
+++ b/src/Psl/Dict/filter.php
@@ -14,11 +14,11 @@ use Closure;
  *
  * Example:
  *
- *      Arr\filter(['', '0', 'a', 'b'])
- *      => Arr('a', 'b')
+ *      Dict\filter(['', '0', 'a', 'b'])
+ *      => Dict(2 => 'a', 3 => 'b')
  *
- *      Arr\filter(['foo', 'bar', 'baz', 'qux'], fn(string $value): bool => Str\contains($value, 'a'));
- *      => Arr('bar', 'baz')
+ *      Dict\filter(['foo', 'bar', 'baz', 'qux'], fn(string $value): bool => Str\contains($value, 'a'));
+ *      => Dict(1 => 'bar', 2 => 'baz')
  *
  * @psalm-template Tk of array-key
  * @psalm-template Tv
diff --git a/src/Psl/Dict/filter_keys.php b/src/Psl/Dict/filter_keys.php
index 9bd373e..c6c1983 100644
--- a/src/Psl/Dict/filter_keys.php
+++ b/src/Psl/Dict/filter_keys.php
@@ -7,18 +7,18 @@ namespace Psl\Dict;
 use Closure;
 
 /**
- * Returns an array containing only the keys for which the given predicate
+ * Returns a dict containing only the keys for which the given predicate
  * returns `true`.
  *
  * The default predicate is casting the key to boolean.
  *
  * Example:
  *
- *      Arr\filter_keys([0 => 'a', 1 => 'b'])
- *      => Arr(1 => 'b')
+ *      Dict\filter_keys([0 => 'a', 1 => 'b'])
+ *      => Dict(1 => 'b')
  *
- *      Arr\filter_keys([0 => 'a', 1 => 'b', 2 => 'c'], fn(int $key): bool => $key <= 1);
- *      => Arr(0 => 'a', 1 => 'b')
+ *      Dict\filter_keys([0 => 'a', 1 => 'b', 2 => 'c'], fn(int $key): bool => $key <= 1);
+ *      => Dict(0 => 'a', 1 => 'b')
  *
  * @psalm-template Tk of array-key
  * @psalm-template Tv
diff --git a/src/Psl/Dict/filter_nulls.php b/src/Psl/Dict/filter_nulls.php
new file mode 100644
index 0000000..08c19f2
--- /dev/null
+++ b/src/Psl/Dict/filter_nulls.php
@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Dict;
+
+/**
+ * Filter out null values from the given iterable.
+ *
+ * Example:
+ *      Dict\filter_nulls([1, null, 5])
+ *      => Dict(0 => 1, 2 => 5)
+ *
+ * @psalm-template Tk of array-key
+ * @psalm-template Tv
+ *
+ * @psalm-param iterable<Tk, Tv|null> $iterable
+ *
+ * @psalm-return array<Tk, Tv>
+ */
+function filter_nulls(iterable $iterable): array
+{
+    /** @var array<Tk, Tv> $result */
+    $result = [];
+    foreach ($iterable as $key => $value) {
+        if (null !== $value) {
+            $result[$key] = $value;
+        }
+    }
+
+    return $result;
+}
diff --git a/src/Psl/Dict/filter_with_key.php b/src/Psl/Dict/filter_with_key.php
index 6148e14..0364171 100644
--- a/src/Psl/Dict/filter_with_key.php
+++ b/src/Psl/Dict/filter_with_key.php
@@ -14,14 +14,14 @@ use Psl;
  *
  * Example:
  *
- *      Arr\filter_with_key(['a', '0', 'b', 'c'])
- *      => Iter('b', 'c')
+ *      Dict\filter_with_key(['a', '0', 'b', 'c'])
+ *      => Dict(2 => 'b', 3 => 'c')
  *
- *      Arr\filter_with_key(
+ *      Dict\filter_with_key(
  *          ['foo', 'bar', 'baz', 'qux'],
  *          fn(int $key, string $value): bool => $key > 1 && Str\contains($value, 'a')
  *      );
- *      => Arr('baz')
+ *      => Dict(2 => 'baz')
  *
  * @psalm-template Tk of array-key
  * @psalm-template Tv
diff --git a/src/Psl/Internal/Loader.php b/src/Psl/Internal/Loader.php
index d5059ca..d5ed75d 100644
--- a/src/Psl/Internal/Loader.php
+++ b/src/Psl/Internal/Loader.php
@@ -102,6 +102,7 @@ final class Loader
         'Psl\Dict\drop_while',
         'Psl\Dict\equal',
         'Psl\Dict\filter',
+        'Psl\Dict\filter_nulls',
         'Psl\Dict\filter_keys',
         'Psl\Dict\filter_with_key',
         'Psl\Dict\flatten',
@@ -199,12 +200,17 @@ final class Loader
         'Psl\Vec\concat',
         'Psl\Vec\enumerate',
         'Psl\Vec\fill',
+        'Psl\Vec\filter',
+        'Psl\Vec\filter_keys',
         'Psl\Vec\filter_nulls',
+        'Psl\Vec\filter_with_key',
         'Psl\Vec\flat_map',
         'Psl\Vec\keys',
         'Psl\Vec\partition',
         'Psl\Vec\range',
         'Psl\Vec\reductions',
+        'Psl\Vec\map',
+        'Psl\Vec\map_with_key',
         'Psl\Vec\reproduce',
         'Psl\Vec\reverse',
         'Psl\Vec\shuffle',
diff --git a/src/Psl/Vec/filter.php b/src/Psl/Vec/filter.php
new file mode 100644
index 0000000..4200745
--- /dev/null
+++ b/src/Psl/Vec/filter.php
@@ -0,0 +1,42 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Vec;
+
+use Closure;
+
+/**
+ * Returns a vec containing only the values for which the given predicate
+ * returns `true`.
+ *
+ * The default predicate is casting the value to boolean.
+ *
+ * Example:
+ *
+ *      Vec\filter(['', '0', 'a', 'b'])
+ *      => Vec('a', 'b')
+ *
+ *      Vec\filter(['foo', 'bar', 'baz', 'qux'], fn(string $value): bool => Str\contains($value, 'a'));
+ *      => Vec('bar', 'baz')
+ *
+ * @psalm-template T
+ *
+ * @psalm-param iterable<T>                 $iterable
+ * @psalm-param (callable(T): bool)|null    $predicate
+ *
+ * @psalm-return list<T>
+ */
+function filter(iterable $iterable, ?callable $predicate = null): array
+{
+    /** @psalm-var (callable(T): bool) $predicate */
+    $predicate = $predicate ?? Closure::fromCallable('Psl\Internal\boolean');
+    $result    = [];
+    foreach ($iterable as $v) {
+        if ($predicate($v)) {
+            $result[] = $v;
+        }
+    }
+
+    return $result;
+}
diff --git a/src/Psl/Vec/filter_keys.php b/src/Psl/Vec/filter_keys.php
new file mode 100644
index 0000000..93be422
--- /dev/null
+++ b/src/Psl/Vec/filter_keys.php
@@ -0,0 +1,43 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Vec;
+
+use Closure;
+
+/**
+ * Returns a vec containing only the values for which the given predicate
+ * returns `true`.
+ *
+ * The default predicate is casting the key to boolean.
+ *
+ * Example:
+ *
+ *      Vec\filter_keys([0 => 'a', 1 => 'b'])
+ *      => Vec('b')
+ *
+ *      Vec\filter_keys([0 => 'a', 1 => 'b', 2 => 'c'], fn(int $key): bool => $key <= 1);
+ *      => Vec('a', 'b')
+ *
+ * @psalm-template Tk
+ * @psalm-template Tv
+ *
+ * @psalm-param iterable<Tk, Tv>           $iterable
+ * @psalm-param (callable(Tk): bool)|null  $predicate
+ *
+ * @psalm-return list<Tv>
+ */
+function filter_keys(iterable $iterable, ?callable $predicate = null): array
+{
+    /** @psalm-var (callable(Tk): bool) $predicate */
+    $predicate = $predicate ?? Closure::fromCallable('Psl\Internal\boolean');
+    $result    = [];
+    foreach ($iterable as $k => $v) {
+        if ($predicate($k)) {
+            $result[] = $v;
+        }
+    }
+
+    return $result;
+}
diff --git a/src/Psl/Vec/filter_with_key.php b/src/Psl/Vec/filter_with_key.php
new file mode 100644
index 0000000..fa94d3c
--- /dev/null
+++ b/src/Psl/Vec/filter_with_key.php
@@ -0,0 +1,51 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Vec;
+
+use Psl;
+
+/**
+ * Returns a vec containing only the values for which the given predicate
+ * returns `true`.
+ *
+ * The default predicate is casting the value to boolean.
+ *
+ * Example:
+ *
+ *      Vec\filter_with_key(['a', '0', 'b', 'c'])
+ *      => Vec('b', 'c')
+ *
+ *      Vec\filter_with_key(
+ *          ['foo', 'bar', 'baz', 'qux'],
+ *          fn(int $key, string $value): bool => $key > 1 && Str\contains($value, 'a')
+ *      );
+ *      => Vec('baz')
+ *
+ * @psalm-template Tk
+ * @psalm-template Tv
+ *
+ * @psalm-param iterable<Tk, Tv>                $iterable
+ * @psalm-param (callable(Tk, Tv): bool)|null   $predicate
+ *
+ * @psalm-return list<Tv>
+ */
+function filter_with_key(iterable $iterable, ?callable $predicate = null): array
+{
+    $predicate = $predicate ??
+        /**
+         * @psalm-param Tk $k
+         * @psalm-param Tv $v
+         */
+        static fn ($k, $v): bool => Psl\Internal\boolean($v);
+
+    $result = [];
+    foreach ($iterable as $k => $v) {
+        if ($predicate($k, $v)) {
+            $result[] = $v;
+        }
+    }
+
+    return $result;
+}
diff --git a/src/Psl/Vec/map.php b/src/Psl/Vec/map.php
new file mode 100644
index 0000000..f3eeb4f
--- /dev/null
+++ b/src/Psl/Vec/map.php
@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Vec;
+
+/**
+ * Applies a mapping function to all values of an iterable.
+ *
+ * The function is passed the current iterable value and should return a
+ * modified value.
+ *
+ * Examples:
+ *
+ *     Vec\map([1, 2, 3, 4, 5], fn($i) => $i * 2);
+ *     => Vec(2, 4, 6, 8, 10)
+ *
+ * @psalm-template Tk
+ * @psalm-template Tv
+ * @psalm-template T
+ *
+ * @psalm-param iterable<Tk, Tv>   $iterable Iterable to be mapped over
+ * @psalm-param (callable(Tv): T)  $function
+ *
+ * @psalm-return list<T>
+ */
+function map(iterable $iterable, callable $function): array
+{
+    $result = [];
+    foreach ($iterable as $value) {
+        $result[] = $function($value);
+    }
+
+    return $result;
+}
diff --git a/src/Psl/Vec/map_with_key.php b/src/Psl/Vec/map_with_key.php
new file mode 100644
index 0000000..6b1b188
--- /dev/null
+++ b/src/Psl/Vec/map_with_key.php
@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Vec;
+
+/**
+ * Applies a mapping function to all values of an iterable.
+ *
+ * The function is passed the current iterable key and value and should return a
+ * modified value.
+ *
+ * Examples:
+ *
+ *     Vec\map_with_key([1, 2, 3, 4, 5], fn($k, $v) => $k + $v);
+ *     => Vec(1, 3, 5, 7, 9)
+ *
+ * @psalm-template Tk
+ * @psalm-template Tv
+ * @psalm-template T
+ *
+ * @psalm-param iterable<Tk, Tv>       $iterable Iterable to be mapped over
+ * @psalm-param (callable(Tk,Tv): T)   $function
+ *
+ * @psalm-return list<T>
+ */
+function map_with_key(iterable $iterable, callable $function): array
+{
+    $result = [];
+    foreach ($iterable as $key => $value) {
+        $result[] = $function($key, $value);
+    }
+
+    return $result;
+}
diff --git a/tests/Psl/Dict/FilterNullsTest.php b/tests/Psl/Dict/FilterNullsTest.php
new file mode 100644
index 0000000..b190a22
--- /dev/null
+++ b/tests/Psl/Dict/FilterNullsTest.php
@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Tests\Dict;
+
+use PHPUnit\Framework\TestCase;
+use Psl\Collection;
+use Psl\Dict;
+use Psl\Iter;
+
+final class FilterNullsTest extends TestCase
+{
+    public function testFilterNulls(): void
+    {
+        static::assertCount(0, Dict\filter_nulls([]));
+        static::assertCount(0, Dict\filter_nulls([null, null]));
+        static::assertCount(1, Dict\filter_nulls([null, false]));
+        static::assertCount(1, Dict\filter_nulls([null, 'null']));
+        static::assertCount(1, Dict\filter_nulls(['null']));
+        static::assertCount(1, Dict\filter_nulls(Iter\Iterator::create(['null'])));
+        static::assertCount(0, Dict\filter_nulls(Iter\Iterator::create([null])));
+        static::assertCount(0, Dict\filter_nulls(Iter\Iterator::create([null, null])));
+        static::assertCount(3, Dict\filter_nulls(Iter\Iterator::create([null, false, '', 0])));
+        static::assertCount(3, Dict\filter_nulls(new Collection\Vector([null, false, '', 0])));
+        static::assertCount(3, Dict\filter_nulls(new Collection\Map([null, false, '', 0])));
+        static::assertCount(3, Dict\filter_nulls((static function (): iterable {
+            yield null;
+            yield false;
+            yield '';
+            yield 0;
+            yield null;
+        })()));
+    }
+}
diff --git a/tests/Psl/Vec/ChunkTest.php b/tests/Psl/Vec/ChunkTest.php
new file mode 100644
index 0000000..55cd0ae
--- /dev/null
+++ b/tests/Psl/Vec/ChunkTest.php
@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Tests\Vec;
+
+use PHPUnit\Framework\TestCase;
+use Psl\Vec;
+
+final class ChunkTest extends TestCase
+{
+    /**
+     * @psalm-template T
+     *
+     * @psalm-param list<list<T>> $expected
+     * @psalm-param iterable<T> $iterable
+     *
+     * @dataProvider provideData
+     */
+    public function testChunk(array $expected, iterable $iterable, int $size): void
+    {
+        static::assertSame($expected, Vec\chunk($iterable, $size));
+    }
+
+    public function provideData(): iterable
+    {
+        yield [[[1], [2], [3]], Vec\range(1, 3), 1];
+        yield [[], [], 4];
+        yield [[[1, 2, 3], [4, 5, 6], [7, 8, 9]], Vec\range(1, 9), 3];
+        yield [[[1, 3, 5], [7, 9]], Vec\range(1, 9, 2), 3];
+        yield [[[1, 3], [5, 7], [9]], Vec\range(1, 9, 2), 2];
+    }
+}
diff --git a/tests/Psl/Vec/FilterKeysTest.php b/tests/Psl/Vec/FilterKeysTest.php
new file mode 100644
index 0000000..69145bb
--- /dev/null
+++ b/tests/Psl/Vec/FilterKeysTest.php
@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Tests\Vec;
+
+use PHPUnit\Framework\TestCase;
+use Psl\Vec;
+
+final class FilterKeysTest extends TestCase
+{
+    /**
+     * @dataProvider provideData
+     */
+    public function testFilter(array $expected, array $array, ?callable $predicate = null): void
+    {
+        $result = Vec\filter_keys($array, $predicate);
+
+        static::assertSame($expected, $result);
+    }
+
+    public function provideData(): iterable
+    {
+        yield  [[], []];
+        yield  [['b'], ['a', 'b']];
+        yield  [['a'], ['a', 'b'], static fn (int $k): bool => $k !== 1];
+        yield  [['b'], ['a', 'b'], static fn (int $k): bool => $k !== 0];
+        yield  [[], ['a', 'b'], static fn (int $_) => false];
+        yield  [['a', 'b'], ['a', 'b'], static fn (int $_): bool => true];
+    }
+}
diff --git a/tests/Psl/Vec/FilterTest.php b/tests/Psl/Vec/FilterTest.php
new file mode 100644
index 0000000..d46b3f1
--- /dev/null
+++ b/tests/Psl/Vec/FilterTest.php
@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Tests\Vec;
+
+use PHPUnit\Framework\TestCase;
+use Psl\Vec;
+
+final class FilterTest extends TestCase
+{
+    /**
+     * @dataProvider provideData
+     */
+    public function testFilter(array $expected, array $array, ?callable $predicate = null): void
+    {
+        $result = Vec\filter($array, $predicate);
+
+        static::assertSame($expected, $result);
+    }
+
+    public function provideData(): iterable
+    {
+        yield  [[], []];
+        yield  [['a', 'b'], ['a', 'b']];
+        yield  [[], ['a', 'b'], static fn () => false];
+        yield  [['a', 'b'], ['a', 'b'], static fn (string $_): bool => true];
+        yield  [['a'], ['a', 'b'], static fn (string $v): bool => 'b' !== $v];
+    }
+}
diff --git a/tests/Psl/Vec/FilterWithKeyTest.php b/tests/Psl/Vec/FilterWithKeyTest.php
new file mode 100644
index 0000000..5dd8e6c
--- /dev/null
+++ b/tests/Psl/Vec/FilterWithKeyTest.php
@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Tests\Vec;
+
+use PHPUnit\Framework\TestCase;
+use Psl\Vec;
+
+final class FilterWithKeyTest extends TestCase
+{
+    /**
+     * @dataProvider provideData
+     */
+    public function testFilterWithKey(array $expected, array $array, ?callable $predicate = null): void
+    {
+        $result = Vec\filter_with_key($array, $predicate);
+
+        static::assertSame($expected, $result);
+    }
+
+    public function provideData(): iterable
+    {
+        yield  [[], []];
+        yield  [['a', 'b'], ['a', 'b']];
+        yield  [[], ['a', 'b'], static fn (int $_k, string $_v) => false];
+        yield  [['a', 'b'], ['a', 'b'], static fn (int $_k, string $_v): bool => true];
+        yield  [['a'], ['a', 'b'], static fn (int $k, string $v): bool => 'b' !== $v];
+        yield  [[], ['a', 'b'], static fn (int $k, string $v): bool => 'b' !== $v && 0 !== $k];
+        yield  [['a'], ['a', 'b'], static fn (int $k, string $v): bool => 'b' !== $v && 1 !== $k];
+        yield  [[], ['a', 'b'], static fn (int $k, string $v): bool => 'a' !== $v && 1 !== $k];
+        yield  [['b'], ['a', 'b'], static fn (int $k, string $v): bool => 'a' !== $v && 0 !== $k];
+    }
+}
diff --git a/tests/Psl/Vec/MapTest.php b/tests/Psl/Vec/MapTest.php
new file mode 100644
index 0000000..72881a2
--- /dev/null
+++ b/tests/Psl/Vec/MapTest.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Tests\Vec;
+
+use PHPUnit\Framework\TestCase;
+use Psl\Vec;
+
+final class MapTest extends TestCase
+{
+    /**
+     * @dataProvider provideData
+     */
+    public function testMap(array $expected, array $array, callable $function): void
+    {
+        $result = Vec\map($array, $function);
+
+        static::assertSame($expected, $result);
+    }
+
+    public function provideData(): iterable
+    {
+        yield [[1, 2, 3], [1, 2, 3], static fn (int $v): int => $v];
+        yield [[2, 4, 6], [1, 2, 3], static fn (int $v): int => $v * 2];
+        yield [['1', '2', '3'], [1, 2, 3], static fn (int $v): string => (string)$v];
+        yield [[], [], static fn (int $v): string => (string)$v];
+    }
+}
diff --git a/tests/Psl/Vec/MapWithKeyTest.php b/tests/Psl/Vec/MapWithKeyTest.php
new file mode 100644
index 0000000..6574ff3
--- /dev/null
+++ b/tests/Psl/Vec/MapWithKeyTest.php
@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Tests\Vec;
+
+use PHPUnit\Framework\TestCase;
+use Psl\Vec;
+
+final class MapWithKeyTest extends TestCase
+{
+    /**
+     * @dataProvider provideData
+     */
+    public function testMapWithKey(array $expected, array $array, callable $function): void
+    {
+        $result = Vec\map_with_key($array, $function);
+        
+        static::assertSame($expected, $result);
+    }
+
+    public function provideData(): iterable
+    {
+        yield [[1, 2, 3], ['a' => 1, 'b' => 2, 'c' => 3], static fn (string $k, int $v): int => $v];
+        yield [[1, 3, 5], [1, 2, 3], static fn (int $k, int $v): int => $k + $v];
+        yield [[0, 4, 16], [1, 2, 3], static fn (int $k, int $v): int => $k * (2 ** $v)];
+        yield [['1', '3', '5'], [1, 2, 3], static fn (int $k, int $v): string => (string) ($k + $v)];
+        yield [[], [], static fn (int $k, int $v): string => (string) ($k + $v)];
+    }
+}
diff --git a/tests/Psl/Vec/ZipTest.php b/tests/Psl/Vec/ZipTest.php
new file mode 100644
index 0000000..1a1ccc0
--- /dev/null
+++ b/tests/Psl/Vec/ZipTest.php
@@ -0,0 +1,40 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Tests\Vec;
+
+use PHPUnit\Framework\TestCase;
+use Psl\Vec;
+
+final class ZipTest extends TestCase
+{
+    /**
+     * @dataProvider provideData
+     */
+    public function testZip(array $expected, array $first, array $second): void
+    {
+        static::assertSame($expected, Vec\zip($first, $second));
+    }
+
+    public function provideData(): iterable
+    {
+        yield [
+            [['foo', 'baz'], ['bar', 'qux']],
+            ['foo', 'bar'],
+            ['baz', 'qux']
+        ];
+
+        yield [
+            [],
+            [],
+            [],
+        ];
+
+        yield [
+            [],
+            ['foo', 'bar'],
+            [],
+        ];
+    }
+}