Dear all, I would like to use boost.xpressive to parse some string like “a+b:c”, and I wrote the following snippet: sregex reOp = as_xpr('+') | '-' | '*' | '/'; sregex reDelim = as_xpr(':'); sregex reField = +_w; sregex reSimpleToken = reOp | reDelim | reField; string str = "a+b:c"; sregex_token_iterator cur(str.begin(), str.end(), reSimpleToken), end; for (; cur != end; ++cur) { cout << *cur << endl; } which will print: a + b : c but I would also want to know which rule is matched for the sequent operations, for example ‘a’, ‘b’ and ‘c' are matched by reField, and ‘+’ is matched by ‘reOp’. I am very new to boost.xpressive, so if this is not the good way, correct me please. Any help is appreciated! Best, Li