public function CustomFunctionsReturningNumerics()
{
$funcName = strtolower($this->_lexer->lookahead['value']);
// getCustomNumericFunction is case-insensitive
$funcClass = $this->_em->getConfiguration()->getCustomNumericFunction($funcName);
$function = new $funcClass($funcName);
$function->parse($this);
return $function;
}