code: public function execute(array $arguments) {
  		//check number of parameters
  		if (empty($arguments)) throw new \BadFunctionCallException("IsType: No arguments found.");
  		
  		foreach ($arguments as $arg) {
  			if (call_user_func($this->callback, $arg) === false) return false;
  		}
  		
  		return true;
  	}
docs: Determines if a value is of a given type
  Usage: (integer? 'hey') (string? _val) (null? _val1 _val2)
  Returns: boolean
  (non-PHPdoc)
  @see \eMacros\Runtime\GenericFunction::execute()