Good morning, I'm trying to parse a relatively simple pattern across 4 std::strings, extracting whatever the part which matches the pattern into a separate std::string. In an abstracted sense, here is what I want: s1=<string1><consecutive number>, s2=<consecutive number><string2>, s3=<string1><consecutive number>, s4=<consecutive number><string2> Less abstracted: s1="apple 1", s2="2 cheese", s3="apple 3", s4="4 cheese" Actual contents: s1="lxckvjlxcjvlkjlkje xvcjxzlvcj wqrej lxvcjz ljvl;x czvouzxvcu j;ljfds apple 1 xcvljxclvjx oueroi xcvzlkjv; zjx", s2="xzljlkxvc jlkjxzvl jxcvljzx lvjlkj wre 2 cheese", s3="apple 3", s4="kxclvj xcvjlxk jcvljxlck jxcvl 4 cheese" How would I perform this pattern matching? Thanks for all suggestions, Alec Taylor
2011/11/10 Alec Taylor <alec.taylor6@gmail.com>
Good morning,
I'm trying to parse a relatively simple pattern across 4 std::strings, extracting whatever the part which matches the pattern into a separate std::string.
In an abstracted sense, here is what I want: s1=<string1><consecutive number>, s2=<consecutive number><string2>, s3=<string1><consecutive number>, s4=<consecutive number><string2>
Less abstracted: s1="apple 1", s2="2 cheese", s3="apple 3", s4="4 cheese"
Actual contents: s1="lxckvjlxcjvlkjlkje xvcjxzlvcj wqrej lxvcjz ljvl;x czvouzxvcu j;ljfds apple 1 xcvljxclvjx oueroi xcvzlkjv; zjx", s2="xzljlkxvc jlkjxzvl jxcvljzx lvjlkj wre 2 cheese", s3="apple 3", s4="kxclvj xcvjlxk jcvljxlck jxcvl 4 cheese"
How would I perform this pattern matching?
Wouldn't Boost.Regex be more appropriate?
I'm not sure which library to use, or how to use them. I have been told on freenode though, that what I want goes past the capabilities of regex. I am skeptical though, which is (in part) why I'm asking here. So how could this be done in boost regex? Thanks :) On Thu, Nov 10, 2011 at 8:17 AM, TONGARI <tongari95@gmail.com> wrote:
2011/11/10 Alec Taylor <alec.taylor6@gmail.com>
Good morning,
I'm trying to parse a relatively simple pattern across 4 std::strings, extracting whatever the part which matches the pattern into a separate std::string.
In an abstracted sense, here is what I want: s1=<string1><consecutive number>, s2=<consecutive number><string2>, s3=<string1><consecutive number>, s4=<consecutive number><string2>
Less abstracted: s1="apple 1", s2="2 cheese", s3="apple 3", s4="4 cheese"
Actual contents: s1="lxckvjlxcjvlkjlkje xvcjxzlvcj wqrej lxvcjz ljvl;x czvouzxvcu j;ljfds apple 1 xcvljxclvjx oueroi xcvzlkjv; zjx", s2="xzljlkxvc jlkjxzvl jxcvljzx lvjlkj wre 2 cheese", s3="apple 3", s4="kxclvj xcvjlxk jcvljxlck jxcvl 4 cheese"
How would I perform this pattern matching?
Wouldn't Boost.Regex be more appropriate?
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I'm trying to parse a relatively simple pattern across 4 std::strings, extracting whatever the part which matches the pattern into a separate std::string.
In an abstracted sense, here is what I want: s1=<string1><consecutive number>, s2=<consecutive number><string2>, s3=<string1><consecutive number>, s4=<consecutive number><string2>
Less abstracted: s1="apple 1", s2="2 cheese", s3="apple 3", s4="4 cheese"
Actual contents: s1="lxckvjlxcjvlkjlkje xvcjxzlvcj wqrej lxvcjz ljvl;x czvouzxvcu j;ljfds apple 1 xcvljxclvjx oueroi xcvzlkjv; zjx", s2="xzljlkxvc jlkjxzvl jxcvljzx lvjlkj wre 2 cheese", s3="apple 3", s4="kxclvj xcvjlxk jcvljxlck jxcvl 4 cheese"
How would I perform this pattern matching?
Use Spirit. I'm not sure I understand your grammar well, but try the following trivial sample: #include <boost/spirit/include/qi.hpp> namespace qi = boost::spirit::qi; using qi::char_; using qi::parse; int main() { std::string input = "abcd apple 1 qwerty", output; bool res = parse(input.begin(), input.end(), qi::omit[*(char_ - (+char_("a-zA-Z") >> ' ' >> +char_("0-9")))] >> +char_("a-zA-Z") >> qi::string(" ") >> +char_("0-9"), output); }
Alec Taylor <alec.taylor6@gmail.com> writes:
I'm trying to parse a relatively simple pattern across 4 std::strings, extracting whatever the part which matches the pattern into a separate std::string.
In an abstracted sense, here is what I want: s1=<string1><consecutive number>, s2=<consecutive number><string2>, s3=<string1><consecutive number>, s4=<consecutive number><string2>
Less abstracted: s1="apple 1", s2="2 cheese", s3="apple 3", s4="4 cheese"
Just to be clear, what do you want in the result string? Without losing data, I believe you could just output: first_num string1 string2
How would I perform this pattern matching?
I'd suggest splitting the responsiblity between regex and your own code. This lets you use regex for what it's good at, and then use procedural code for what *it* is good at. (I ran into this all the time in perl: people would try to do *everything* in the regex, when it was often much cleaner to do some of the work in procedural code outside the RE.) Anyway, find my attempt below. Best Regards, Tony ---------------------------------------------------------------------- // compile line: // g++ -o substr-regex substr-regex.cpp -lboost_regex #include <iostream> #include <string> #include <boost/lexical_cast.hpp> #include <boost/regex.hpp> #include <boost/test/minimal.hpp> namespace { bool do_one_match( const std::string & in, const boost::regex & re, std::string & m1, std::string & m2 ) { boost::smatch matches; if ( regex_match( in, matches, re ) ) { m1 = matches[1]; m2 = matches[2]; return true; } else { return false; } } const std::string num_pat ( "(\\d+)" ); const std::string str_pat ( "(.+?)" ); const std::string ws_pat ( "\\s+" ); const boost::regex num_str_re( num_pat + ws_pat + str_pat ); const boost::regex str_num_re( str_pat + ws_pat + num_pat ); bool do_match( const std::string & s1, const std::string & s2, const std::string & s3, const std::string & s4, std::string & result ) { std::string s1_num, s1_str; if ( ! do_one_match( s1, str_num_re, s1_str, s1_num ) ) return false; std::string s2_str, s2_num; if ( ! do_one_match( s2, num_str_re, s2_num, s2_str ) ) return false; int s1_val( boost::lexical_cast< int >( s1_num ) ); int s2_val( boost::lexical_cast< int >( s2_num ) ); if ( s2_val != s1_val + 1 ) return false; std::string s3_num, s3_str; if ( ! do_one_match( s3, str_num_re, s3_str, s3_num ) ) return false; if ( s3_str != s1_str ) return false; int s3_val( boost::lexical_cast< int >( s3_num ) ); if ( s3_val != s2_val + 1 ) return false; std::string s4_str, s4_num; if ( ! do_one_match( s4, num_str_re, s4_num, s4_str ) ) return false; if ( s4_str != s2_str ) return false; int s4_val( boost::lexical_cast< int >( s4_num ) ); if ( s4_val != s3_val + 1 ) return false; result = s1_num + " " + s1_str + " " + s2_str; return true; } } int test_main( int argc, char * argv[] ) { std::string s1( "apple 1" ); std::string s2( "2 cheese" ); std::string s3( "apple 3" ); std::string s4( "4 cheese" ); std::string result; BOOST_CHECK( do_match( s1, s2, s3, s4, result ) ); BOOST_CHECK( result == "1 apple cheese" ); s4 = "5 cheese"; BOOST_CHECK( ! do_match( s1, s2, s3, s4, result ) ); s4 = "4 steak"; BOOST_CHECK( ! do_match( s1, s2, s3, s4, result ) ); return boost::exit_success; }
participants (4)
-
Alec Taylor -
Anthony Foiani -
Igor R -
TONGARI