Merge pull request #105 from ilario-pierbattista/ilario-pierbattista-pipe-function

Introduction of the pipe function inspired by fp-ts

Author: widmogrod

src/Functional/miscellaneous.php

@@ -87,8 +87,8 @@ function compose(callable $a, callable $b)
  * Composition starts from left.
  *
  * <code>
- * compose('strtolower', 'strtoupper')('aBc') ≡ 'ABC'
- * strtouppser(strtolower('aBc'))  ≡ 'ABC'
+ * pipeline('strtolower', 'strtoupper')('aBc') ≡ 'ABC'
+ * strtoupper(strtolower('aBc'))  ≡ 'ABC'
  * </code>
  *
  * @param callable $a
@@ -107,6 +107,37 @@ function pipeline(callable $a, callable $b)
     };
 }
 
+/**
+ * @var callable
+ */
+const pipe = 'Widmogrod\Functional\pipe';
+
+/**
+ * The first argument becomes the input of the composition
+ * of functions given as arguments following the former.
+ * Composition stats from left.
+ *
+ * <code>
+ * pipe('aBc', 'strtolower', 'strtoupper') ≡ 'ABC'
+ * strtoupper(strtolower('aBc')) ≡ 'ABC'
+ * </code>
+ *
+ * @param  mixed    $in
+ * @param  callable $fab
+ * @param  callable ...$fbc
+ * @return mixed
+ */
+function pipe(
+    $in,
+    callable $fab,
+    callable ...$fbc
+) {
+    $callables = count($fbc) > 0
+        ? $fbc
+        : [identity];
+
+    return pipeline($fab, ...$callables)($in);
+}
 
 /**
  * @var callable

test/Functional/PipeTest.php

@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace test\Functional;
+
+use Widmogrod\Functional as f;
+
+class PipeTest extends \PHPUnit\Framework\TestCase
+{
+    /**
+     * @dataProvider provideData
+     */
+    public function test_it_should_compose_and_inject_input_correctly(
+        $functions,
+        $value,
+        $expected
+    ) {
+        $this->assertEquals(
+            $expected,
+            f\pipe($value, ...$functions)
+        );
+    }
+
+    public function provideData()
+    {
+        return [
+            'two function' => [
+                '$functions' => ['strtolower', 'strtoupper'],
+                '$value' => 'aBcD',
+                '$expected' => 'ABCD'
+            ],
+        ];
+    }
+}