86      * @param   string  $name     Constant name.
91     public function addConstant($name, $value)  argument
93         if (true === $this->_constants->offsetExists($name)) {
97                 $name
101         $this->_constants[$name] = $value;
109      * @param   string  $name    Constant name.
113     public function getConstant($name)  argument
115         if (false === $this->_constants->offsetExists($name)) {
119                 $name
123         return $this->_constants[$name];
139      * @param   string  $name        Function name.
144     public function addFunction($name, $callable = null)  argument
147             if (false === function_exists($name)) {
151                     $name
155             $callable = $name;
158         $this->_functions[$name] = xcallable($callable);
166      * @param   string  $name    Function name.
170     public function getFunction($name)  argument
172         if (false === $this->_functions->offsetExists($name)) {
176                 $name
180         return $this->_functions[$name];
196      * @param   string    $name        Variable name.
200     public function addVariable($name, callable $callable)  argument
202         $this->_variables[$name] = xcallable($callable);
210      * @param   string   $name    Variable name.
214     public function getVariable($name)  argument
216         if (false === $this->_variables->offsetExists($name)) {
220                 $name
224         return $this->_variables[$name]($this);