Access regex_id from semantic action

[zeratul976@…]

It would be useful to be able to access from a semantic action the regex_id of the regex to which the semantic action belongs.

I propose a special symbol named _regex_id_ for this purpose.

Examples:

sregex rx = xpr[cout << _regex_id_];
regex_match(str, rx);  // prints rx.regex_id() on success

sregex sub = xpr[cout << _regex_id_];
sregex rx = sub >> another_xpr;
regex_match(str, rx);  // prints sub.regex_id() on success (not rx.regex_id())