add ref method with arity setting

src/functions.php

@@ -27,31 +27,54 @@ function predicate($predicate): Predicate
         case $predicate instanceof Predicate:
             return $predicate;
         case is_callable($predicate):
-            return new ClosurePredicate(\Closure::fromCallable($predicate));
+            return new ClosurePredicate(closure($predicate));
         default:
             throw new \InvalidArgumentException('$predicate is not valid predicate.');
     }
 }
 
-function ref($callable)
+function closure($callable)
 {
-    if (is_array($callable)) {
+    switch (true) {
+        case $callable instanceof \Closure:
+            return $callable;
+
+        case is_array($callable):
             list($object, $method) = $callable;
             $reflection = new \ReflectionObject($object);
             $method     = $reflection->getMethod($method);
 
             if (!$method->isPublic()) {
-            $class = debug_backtrace()[1]['class'] ?? null;
+                $backtrace = debug_backtrace();
+                foreach ($backtrace as $trace) {
+                    if (isset($trace['class']) && $trace['class'] === $reflection->name) {
+                        break;
+                    }
 
-            if ($reflection->name !== $class) {
+                    if ((isset($trace['class']) && strpos($trace['class'], "Kadet\\Functional\\") !== 0)
+                        || ($trace['function'] && strpos($trace['function'], "Kadet\\Functional\\") !== 0)) {
                         throw new NoAccessException(sprintf('Method "%s" can only be accessed from inside of object.', $method->name));
                     }
                 }
+            }
 
             return $method->getClosure($object);
+
+        default:
+            return \Closure::fromCallable($callable);
+    }
 }
 
-    return \Closure::fromCallable($callable);
+function arify($callable, int $arity)
+{
+    return function (...$args) use ($callable, $arity) {
+        return $callable(...array_slice($args, 0, $arity));
+    };
+}
+
+function ref($callable, ?int $arity = null) {
+    $closure = closure($callable);
+    return $arity !== null ? arify($callable, $arity) : $closure;
 }
 
 function not($predicate)
@@ -101,6 +124,10 @@ function repeat($times, callable $callback)
     }
 }
 
+function identity($x) {
+    return $x;
+}
+
 /**
  * @param callable $callable
  *

tests/ReferencingTest.php

@@ -1,6 +1,7 @@
 <?php
 
 use function Kadet\Functional\apply;
+use function Kadet\Functional\arify;
 use function Kadet\Functional\ref;
 
 /**
@@ -29,8 +30,15 @@ class TestObject
     }
 }
 
-class RandomTest extends \PHPUnit\Framework\TestCase
+class ReferencingTest extends \PHPUnit\Framework\TestCase
 {
+    public function testReferenceClosure()
+    {
+        $f = function () { };
+
+        $this->assertSame($f, ref($f));
+    }
+
     public function testApplicationOfArrayNotation()
     {
         $object = new TestObject();
@@ -54,4 +62,32 @@ class RandomTest extends \PHPUnit\Framework\TestCase
 
         ref([$object, 'priv']);
     }
+
+    public function testSetFunctionArity()
+    {
+        $f = function (...$args) {
+            return count($args);
+        };
+
+        $f = arify($f, 2);
+
+        $this->assertSame(1, $f(1));
+        $this->assertSame(2, $f(1, 2));
+        $this->assertSame(2, $f(1, 2, 3));
+        $this->assertSame(2, $f(1, 2, 3, 4));
+    }
+
+    public function testReferencingWithSpecificArity()
+    {
+        $f = function (...$args) {
+            return count($args);
+        };
+
+        $f = ref($f, 2);
+
+        $this->assertSame(1, $f(1));
+        $this->assertSame(2, $f(1, 2));
+        $this->assertSame(2, $f(1, 2, 3));
+        $this->assertSame(2, $f(1, 2, 3, 4));
+    }
 }