5 files changed, 73 insertions, 22 deletions
diff --git a/src/NXP/Classes/Calculator.php b/src/NXP/Classes/Calculator.php
index 41e0d9f..bfa7015 100644
--- a/src/NXP/Classes/Calculator.php
+++ b/src/NXP/Classes/Calculator.php
@@ -13,6 +13,7 @@ namespace NXP\Classes;
 use NXP\Classes\Token\InterfaceOperator;
 use NXP\Classes\Token\TokenFunction;
 use NXP\Classes\Token\TokenNumber;
+use NXP\Classes\Token\TokenString;
 use NXP\Classes\Token\TokenVariable;
 use NXP\Exception\IncorrectExpressionException;
 use NXP\Exception\UnknownVariableException;
@@ -32,15 +33,18 @@ class Calculator
      */
     public function calculate($tokens, $variables)
     {
-        $stack = array();
+        $stack = [];
         foreach ($tokens as $token) {
             if ($token instanceof TokenNumber) {
                 array_push($stack, $token);
             }
+            if ($token instanceof TokenString) {
+                array_push($stack, $token);
+            }
             if ($token instanceof TokenVariable) {
                 $variable = $token->getValue();
                 if (!array_key_exists($variable, $variables)) {
-                    throw new UnknownVariableException();
+                    throw new UnknownVariableException($variable);
                 }
                 $value = $variables[$variable];
                 array_push($stack, new TokenNumber($value));
diff --git a/src/NXP/Classes/Lexer.php b/src/NXP/Classes/Lexer.php
index e541732..82b2c53 100644
--- a/src/NXP/Classes/Lexer.php
+++ b/src/NXP/Classes/Lexer.php
@@ -17,6 +17,7 @@ use NXP\Classes\Token\TokenLeftBracket;
 use NXP\Classes\Token\TokenNumber;
 use NXP\Classes\Token\TokenRightBracket;
 use NXP\Classes\Token\TokenVariable;
+use NXP\Classes\Token\TokenString;
 use NXP\Exception\IncorrectBracketsException;
 use NXP\Exception\IncorrectExpressionException;
 
@@ -42,7 +43,7 @@ class Lexer
      */
     public function stringToTokensStream($input)
     {
-        $matches = array();
+        $matches = [];
         preg_match_all($this->tokenFactory->getTokenParserRegex(), $input, $matches);
         $tokenFactory = $this->tokenFactory;
         $tokensStream = array_map(
@@ -62,10 +63,13 @@ class Lexer
      */
     public function buildReversePolishNotation($tokensStream)
     {
-        $output = array();
-        $stack = array();
+        $output = [];
+        $stack = [];
 
         foreach ($tokensStream as $token) {
+            if ($token instanceof TokenString) {
+                $output[] = $token;
+            }
             if ($token instanceof TokenNumber) {
                 $output[] = $token;
             }
diff --git a/src/NXP/Classes/Token/TokenFunction.php b/src/NXP/Classes/Token/TokenFunction.php
index 23f64bd..2ed8ace 100644
--- a/src/NXP/Classes/Token/TokenFunction.php
+++ b/src/NXP/Classes/Token/TokenFunction.php
@@ -29,7 +29,7 @@ class TokenFunction extends AbstractContainerToken implements InterfaceFunction
      */
     public function execute(&$stack)
     {
-        $args = array();
+        $args = [];
         list($places, $function) = $this->value;
         for ($i = 0; $i < $places; $i++) {
             array_push($args, array_pop($stack)->getValue());
diff --git a/src/NXP/Classes/Token/TokenString.php b/src/NXP/Classes/Token/TokenString.php
new file mode 100644
index 0000000..cab0711
--- /dev/null
+++ b/src/NXP/Classes/Token/TokenString.php
@@ -0,0 +1,25 @@
+<?php
+/**
+ * This file is part of the MathExecutor package
+ *
+ * (c) Alexander Kiryukhin
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code
+ */
+
+namespace NXP\Classes\Token;
+
+/**
+ * @author Bruce Wells <brucekwells@gmail.com>
+ */
+class TokenString extends AbstractContainerToken
+{
+    /**
+     * @return string
+     */
+    public static function getRegex()
+    {
+        return '"([^"]|"")*"';
+    }
+}
diff --git a/src/NXP/Classes/TokenFactory.php b/src/NXP/Classes/TokenFactory.php
index 19ba1cf..dbe6624 100644
--- a/src/NXP/Classes/TokenFactory.php
+++ b/src/NXP/Classes/TokenFactory.php
@@ -17,6 +17,7 @@ use NXP\Classes\Token\TokenLeftBracket;
 use NXP\Classes\Token\TokenNumber;
 use NXP\Classes\Token\TokenRightBracket;
 use NXP\Classes\Token\TokenVariable;
+use NXP\Classes\Token\TokenString;
 use NXP\Exception\UnknownFunctionException;
 use NXP\Exception\UnknownOperatorException;
 use NXP\Exception\UnknownTokenException;
@@ -31,24 +32,36 @@ class TokenFactory
      *
      * @var array
      */
-    protected $operators = array();
+    protected $operators = [];
 
     /**
      * Available functions
      *
      * @var array
      */
-    protected $functions = array();
+    protected $functions = [];
 
     /**
      * Add function
-     * @param $name
-     * @param $function
-     * @param $places
+     * @param string   $name
+     * @param callable $function
+     * @param int      $places
      */
-    public function addFunction($name, $function, $places = 1)
+    public function addFunction($name, callable $function, $places = 1)
     {
-        $this->functions[$name] = array($places, $function);
+        $this->functions[$name] = [$places, $function];
+    }
+
+
+    /**
+     * get functions
+     *
+     * @return array containing callback and places indexed by
+     *         function name
+     */
+    public function getFunctions()
+    {
+        return $this->functions;
     }
 
     /**
@@ -61,7 +74,7 @@ class TokenFactory
         $class = new \ReflectionClass($operatorClass);
 
         if (!in_array('NXP\Classes\Token\InterfaceToken', $class->getInterfaceNames())) {
-            throw new UnknownOperatorException;
+            throw new UnknownOperatorException($operatorClass);
         }
 
         $this->operators[] = $operatorClass;
@@ -69,13 +82,13 @@ class TokenFactory
     }
 
     /**
-     * Add variable
-     * @param string $name
-     * @param mixed  $value
+     * Get registered operators
+     *
+     * @return array of operator class names
      */
-    public function addVariable($name, $value)
+    public function getOperators()
     {
-
+        return $this->operators;
     }
 
     /**
@@ -89,8 +102,9 @@ class TokenFactory
         }
 
         return sprintf(
-            '/(%s)|([%s])|(%s)|(%s)|([%s%s%s])/i',
+            '/(%s)|(%s)|([%s])|(%s)|(%s)|([%s%s%s])/i',
             TokenNumber::getRegex(),
+            TokenString::getRegex(),
             $operatorsRegex,
             TokenFunction::getRegex(),
             TokenVariable::getRegex(),
@@ -119,6 +133,10 @@ class TokenFactory
             return new TokenRightBracket();
         }
 
+        if ($token[0] == '"') {
+            return new TokenString(str_replace('"', '', $token));
+        }
+
         if ($token == ',') {
             return new TokenComma();
         }
@@ -140,10 +158,10 @@ class TokenFactory
             if (isset($this->functions[$token])) {
                 return new TokenFunction($this->functions[$token]);
             } else {
-                throw new UnknownFunctionException();
+                throw new UnknownFunctionException($token);
             }
         }
 
-        throw new UnknownTokenException();
+        throw new UnknownTokenException($token);
     }
 }