search from the grammar object from the start or end of the specified string
Negative values of nth search from the end of the string.
| std::match | match the grammar object with the start of the specified string |
| std::match_back | match the grammar object with the end of the specified string |
| std_types::character | searches for the character from the start or the end of a string |
| std_types::set | searches for one of the alternatives from the start or the end of a string |
| std_types::string | searches for the start of the string within the stream |