added simple math and charts modules

vendor/andileco/eval-math/src/Stack.php

@@ -0,0 +1,45 @@
+<?php
+/**
+ *
+ */
+
+namespace Andileco\Util\EvalMath;
+
+/**
+ * Class Stack
+ */
+class Stack
+{
+    /**
+     * @var array
+     */
+    public $stack = array();
+
+    /**
+     * @var int
+     */
+    public $count = 0;
+    
+    public function push($val)
+    {
+        $this->stack[$this->count] = $val;
+        $this->count++;
+    }
+    
+    public function pop()
+    {
+        if ($this->count > 0) {
+            $this->count--;
+            return $this->stack[$this->count];
+        }
+
+        return null;
+    }
+    
+    public function last($n=1)
+    {
+        $key = $this->count - $n;
+    		
+        return array_key_exists($key,$this->stack) ? $this->stack[$key] : null;
+    }
+}