Re: [Boost-users] [Xpressive] Baffled about results of search

From: Lynn Allan (l_d_allan_at_[hidden])
Date: 2006-04-12 18:26:25

> A better approach would be to use iterators.
>
> // Begin searching 32 characters into altDow
> regex_search( altDow.begin() + 32, altDow.end(), what, rex )
>
> Note #1: the match results will now contain iterators into altDow, 
> but
> position offsets will be relative to the start of the search, not 
> the
> start of altDow.

Is the following getting closer to "best practice" to use 
xpressive-static for the kinds of specialized searches I'm attempting. 
When I'm further along on the learning curve, I'll try to prepare some 
"apples and apples" timing comparisons between boost::regex, 
xpressive, spirit, a hand-tuned state-machine searcher, and an 
automatic FSM generator utility.

I think I'm conforming to the guidelines on this page:
X:\DevTools\Boost\libs\xpressive\doc\html\boost_xpressive\user_s_guide\tips_n_tricks.html
except I don't understand how to specify
syntax_option_type::optimize
(does it apply to xpressive-static, or only xpressive-dynamic)?

boost::xpressive::regex_constants::syntax_option_type flags =
                     boost::xpressive::regex_constants::optimize;
sregex rexStatic =
    (s1 = (as_xpr("Sunday") | "Sun")) |
    (s2 = (as_xpr("Monday") | "Mon")) |
    (s3 = (as_xpr("Tuesday") | "Tue")) |
    (s4 = (as_xpr("Wednesday") | "Wed")) |
    (s5 = (as_xpr("Thursday") | "Thu")) |
    (s6 = (as_xpr("Friday") | "Fri")) |
    (s7 = (as_xpr("Saturday") | "Sat")) ;

//??? rexStatic.compile(rexStatic, flags);
smatch what;

std::string testStr =
    "Alternate days of the week are Tue and Thursday and Sat and 
Monday. "
    "And then Monday and Wed and Friday and Sun. ";
std::string::const_iterator start = testStr.begin();
std::string::const_iterator finish = testStr.end();
int foundCount = 0;
while (regex_search(start, finish, what, rexStatic)) {
    foundCount++;
    size_t limit = what.size();
    size_t matchIndex = 1;
    while (matchIndex <= limit) {
        if (what[matchIndex].matched == true) {
            break;
        }
        ++matchIndex;
    }
#ifdef _DEBUG
    cout << "FoundCount: " << foundCount
            << " Index: " << static_cast<int>(matchIndex)
            << " what[0]: " << what[0] << endl;
#endif
    start = what[0].second;
}