Add the concat transformer

Author: tomphp

CHANGELOG.md

@@ -4,6 +4,10 @@ This project adheres to [Semantic Versioning](http://semver.org/).<Paste>
 
 ## [Unreleased]
 
+## [0.2.3] - 2016-03-22
+### Added
+- `concat()`
+
 ## [0.2.2] - 2016-03-18
 ### Added
 - `newInstance()`

README.md

@@ -186,6 +186,22 @@ function ($value) {
 }
 ```
 
+#### T\concat(...$arguments)
+
+Use `__` as the placeholder for where you want the value inserted:
+
+```php
+use const TomPHP\Transform\__;
+
+T\concat('Hello ', __, '!');
+
+// Is equivilent to:
+
+function ($value) {
+    return 'Hello ' . $value . '!';
+}
+```
+
 ### Generic Transformations
 
 #### T\argumentTo(callable $callable, array $argments = [__])

src/transform.php

@@ -251,6 +251,22 @@ function append($suffix)
     };
 }
 
+/**
+ * Returns a transformer which concatenates all it's arguments together.
+ *
+ * @param string[] ...$arguments
+ *
+ * @return \Closure
+ */
+function concat(...$arguments)
+{
+    return function ($value) use ($arguments) {
+        $arguments = substituteArguments($arguments, $value);
+
+        return implode('', $arguments);
+    };
+}
+
 /**
  * Returns a transformer which instantiates a $className object on its arguments and
  * returns the result.
@@ -283,3 +299,21 @@ function ($arg) use ($value) {
         return new $className(...$arguments);
     };
 }
+
+/**
+ * @internal
+ *
+ * @param array $arguments
+ * @param mixed $value
+ *
+ * @return array
+ */
+function substituteArguments(array $arguments, $value)
+{
+    return array_map(
+        function ($arg) use ($value) {
+            return $arg === __ ? $value : $arg;
+        },
+        $arguments
+    );
+}

tests/ConcatTest.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace tests\TomPHP\Transform;
+
+use PHPUnit_Framework_TestCase;
+use TomPHP\Transform as T;
+use TomPHP\Transform\Exception\InvalidArgumentException;
+use TomPHP\Transform\Exception\UnexpectedValueException;
+use const TomPHP\Transform\__;
+
+final class ConcatTest extends PHPUnit_Framework_TestCase
+{
+    /** @test */
+    public function it_concatenates_all_the_arguments_together()
+    {
+        $fn = T\concat('abc', 'def', 'ghi');
+
+        $this->assertSame('abcdefghi', $fn('xxx'));
+    }
+
+    /** @test */
+    public function it_inserts_the_value_at_the_placeholder()
+    {
+        $fn = T\concat('abc', __, 'ghi');
+
+        $this->assertSame('abcDEFghi', $fn('DEF'));
+    }
+}