Add concat

Author: mpajunen

docs/Functions.md

@@ -1,6 +1,6 @@
 # Phamda functions
 
-Currently included functions (99):
+Currently included functions (100):
 
 * [_](#_)
 * [add](#add)
@@ -19,6 +19,7 @@ Currently included functions (99):
 * [clone_](#clone_)
 * [comparator](#comparator)
 * [compose](#compose)
+* [concat](#concat)
 * [construct](#construct)
 * [constructN](#constructN)
 * [contains](#contains)
@@ -332,6 +333,18 @@ $upperHello('world'); // => 'HELLO WORLD'
 ```
 
 
+<a name="concat"></a>
+### concat
+`string Phamda::concat(string $a, string $b)`
+
+Returns a string concatenated of `a` and `b`.
+##### Examples
+```php
+Phamda::concat('ab', 'cd'); // => 'abcd'
+Phamda::concat('abc', ''); // => 'abc'
+```
+
+
 <a name="construct"></a>
 ### construct
 `object Phamda::construct(string $class, mixed ... $initialArguments)`

src/Phamda.php

@@ -422,6 +422,26 @@ public static function compose(... $functions)
         return Phamda::pipe(...array_reverse($functions));
     }
 
+    /**
+     * Returns a string concatenated of `a` and `b`.
+     *
+     * ```php
+     * Phamda::concat('ab', 'cd'); // => 'abcd'
+     * Phamda::concat('abc', ''); // => 'abc'
+     * ```
+     *
+     * @param string $a
+     * @param string $b
+     *
+     * @return callable|string
+     */
+    public static function concat($a = null, $b = null)
+    {
+        return static::curry2(function ($a, $b) {
+            return $a . $b;
+        }, func_get_args());
+    }
+
     /**
      * Wraps the constructor of the given class to a function.
      *

tests/BasicProvidersTrait.php

@@ -181,6 +181,14 @@ public function getComposeData()
         ];
     }
 
+    public function getConcatData()
+    {
+        return [
+            ['abcd', 'ab', 'cd'],
+            ['abc', 'abc', ''],
+        ];
+    }
+
     public function getConstructData()
     {
         return [

tests/BasicTest.php

@@ -201,6 +201,18 @@ public function testCompose($expected, array $functions, ... $arguments)
         $this->assertSame($expected, $main0(...$arguments), 'compose produces correct results.');
     }
 
+    /**
+     * @dataProvider getConcatData
+     */
+    public function testConcat($expected, $a, $b)
+    {
+        $this->assertSame($expected, Phamda::concat($a, $b), 'concat produces correct results.');
+        $curried0 = Phamda::concat();
+        $this->assertSame($expected, $curried0($a, $b), 'concat is curried correctly.');
+        $curried1 = Phamda::concat($a);
+        $this->assertSame($expected, $curried1($b), 'concat is curried correctly.');
+    }
+
     /**
      * @dataProvider getContainsData
      */