Convert Math\min to take a Traversable

Summary:
The function formerly known as `Math\min` was renamed to `Math\minv`. This function will replace `C\min`.

See #25.

Reviewed By: fredemmott

Differential Revision: D6096198

fbshipit-source-id: 9f3067b1ba358a8ca6520fe8dbc8e13f09488eda

src/math/containers.php

@@ -97,14 +97,22 @@ function median(Container<num> $numbers): ?float {
 }
 
 /**
- * Returns the smallest of all input numbers.
+ * Returns the smallest element of the given Traversable, or null if the
+ * Traversable is empty.
  *
- * For finding the largest number, see `Math\max`.
- * For Traversables, see `C\min`.
+ * For a known number of inputs, see `Math\minv`.
+ * To find the largest number, see `Math\max`.
  */
-<<__Deprecated('renamed to Math\\minv')>>
-function min<T as num>(T $first_number, T ...$numbers): T {
-  return namespace\minv($first_number, ...$numbers);
+function min<T as num>(
+  Traversable<T> $numbers,
+): ?T {
+  $min = null;
+  foreach ($numbers as $number) {
+    if ($min === null || $number < $min) {
+      $min = $number;
+    }
+  }
+  return $min;
 }
 
 /**

tests/math/MathContainersTest.php

@@ -121,6 +121,37 @@ public function testMedian(
     }
   }
 
+  public static function provideTestMin(): array<mixed> {
+    return array(
+      tuple(
+        array(),
+        null,
+      ),
+      tuple(
+        Set {8, 6, 7, 5, 3, 0, 9},
+        0,
+      ),
+      tuple(
+        HackLibTestTraversables::getIterator(
+          array(8, 6, 7, 5, 3, 0, 9),
+        ),
+        0,
+      ),
+      tuple(
+        Vector {8, 6, 7, -5, -3, 0, 9},
+        -5,
+      ),
+    );
+  }
+
+  /** @dataProvider provideTestMin */
+  public function testMin<T as num>(
+    Traversable<T> $traversable,
+    ?T $expected,
+  ): void {
+    expect(Math\min($traversable))->toBeSame($expected);
+  }
+
   public static function provideTestMinBy(): array<mixed> {
     return array(
       tuple(