Fixed function argument ordering and default parameter type for addFunction

Updated unit tests
Fixed docs

4 files changed, 14 insertions, 6 deletions

diff --git a/README.md b/README.md
index b86f9c6..0c87108 100644
--- a/README.md
+++ b/README.md
@@ -41,11 +41,11 @@ Default functions:
 
 Add custom function to executor:
 ```php
-$executor->addFunction('abs', function($arg) {
-    return abs($arg);
-}, 1);
+$executor->addFunction('abs', function($arg) {return abs($arg);});
 ```
 
+Default parameters are not currently supported.
+
 ## Operators:
 Default operators: `+ - * / ^`
 
@@ -113,7 +113,7 @@ Default variables:
 
 ```
 $pi = 3.14159265359
-$e = 2.71828182846
+$e  = 2.71828182846
 ```
 
 You can add your own variables to executor:
diff --git a/src/NXP/Classes/Token/TokenFunction.php b/src/NXP/Classes/Token/TokenFunction.php
index b2866c3..d61bb5d 100644
--- a/src/NXP/Classes/Token/TokenFunction.php
+++ b/src/NXP/Classes/Token/TokenFunction.php
@@ -32,7 +32,7 @@ class TokenFunction extends AbstractContainerToken implements InterfaceFunction
         $args = [];
         list($places, $function) = $this->value;
         for ($i = 0; $i < $places; $i++) {
-            array_push($args, array_pop($stack)->getValue());
+            $args[] = array_shift($stack)->getValue();
         }
         $result = call_user_func_array($function, $args);
 
diff --git a/src/NXP/MathExecutor.php b/src/NXP/MathExecutor.php
index 29c6a64..6325d35 100644
--- a/src/NXP/MathExecutor.php
+++ b/src/NXP/MathExecutor.php
@@ -174,7 +174,7 @@ class MathExecutor
      * @return MathExecutor
      * @throws \ReflectionException
      */
-    public function addFunction($name, $function = null, $places = 1)
+    public function addFunction($name, $function = null, $places = null)
     {
         $this->tokenFactory->addFunction($name, $function, $places);
 
diff --git a/tests/MathTest.php b/tests/MathTest.php
index 55e0799..d1c9604 100644
--- a/tests/MathTest.php
+++ b/tests/MathTest.php
@@ -146,6 +146,14 @@ class MathTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals($calculator->execute('round(100/30)'), $phpResult);
     }
 
+    public function testFunctionsWithQuotes()
+    {
+        $calculator = new MathExecutor();
+        $calculator->addFunction('concat', function($first, $second){return $first.$second;});
+        $this->assertEquals('testing', $calculator->execute('concat("test", "ing")'));
+        $this->assertEquals('testing', $calculator->execute("concat('test', 'ing')"));
+    }
+
     public function testQuotes()
     {
         $calculator = new MathExecutor();