(iv) The regular expression of the boost library regex

(iv) The regular expression of the boost library regex

The regular expression can bring us great convenience, with it, no longer have to worry about this

Header file:

#include <boost/regex.hpp>

1. Exact match

    std::stringstr("ABCD");   

    Boost::reg("A\\w*d");  

    if (Regex_match (str, REG))

    {

        std::"is matchStd::endl;  

    }

    Else

    {

        STD:: "is not matchStd::endl;  

    }

2. Exactly match and get substring

    "[email protected]"; 

    Boost::cmatch Res;

    Create 3 sub-expressions

    Boost::reg("(\\w+) @(\\w+).  (\\w+) ");

    if (Boost::regex_match (Mail,res, Reg))

    {

        Data can be obtained either through iterators or by array

        for (Boost::cmatch::iterator pos = Res.begin (); pos! = Res.end (); ++pos)

        {

            std::Std::endl;

        }

        RES[0] Store the complete string that matches to

        std::"name:" << res[Std::endl;   

    }

3, find, when you do not need to match the entire string, you can choose to find

    "[email protected]"; 

    Boost::cmatch Res;

    Create 3 sub-expressions

    Boost::reg("(\\w+) @(\\w+).  (\\w+) ");

    if (Boost::regex_search (Mail,res, Reg))

    {

        std::cout <<"**************************************Std::endl;   

        Data can be obtained either through iterators or by array

        for (Boost::cmatch::iterator pos = Res.begin (); pos! = Res.end (); ++pos)

        {

            std::Std::endl;

        }

        RES[0] Store the complete string that matches to

        std::"match:" << res["name:" << res[Std::endl;     

    }

4. Replace

Replace the substring that matches to, you can reference the nth match to the value by $n, $& reference the full match

#include <boost/algorithm/string.hpp>  

Testreplace()

{

    Replace [email protected] with [email protected]

    std::stringmail("[Email protected]");   

    Create 3 sub-expressions

    Boost::reg("(\\w+) @(\\w+).  (\\w+) ");

    std::"[email protected]$3std::endl;  

    std::"[email protected]$2.$3std::endl;  

    Custom substitution function, regex_replace passing a matching string array to the callback function, returning the new string from the callback function

    std::cout << boost::regex_replace (Mail, Reg, [] (const Boost::smatch  &m) { 

        Return boost::to_upper_copy (m[0].str ());

    });

}

5. Iteration

When you need to extract multiple expressions from a string, you can use an iteration to extract

    std::stringstr("[email protected], [email protected], [email protected]");   

    Boost::reg("(\\w+) @(\\w+).  (\\w+) ");

    Boost::pos(Str.begin (), str.end(), Reg);   

    Boost::sregex_iterator end;

    while (pos! = end)

    {

        std::"[" << (*pos) ["]";     

        ++pos;

    }

6. Participle

#include <iostream>

#include <boost/regex.hpp>

Testtoken()

{

    Std

    namespace boost;

    Stringstr("[email protected], [email protected], [email protected]");  

    Reg("\\w+"); 

    POS(Str.begin (), str.end(), Reg);  

    while (pos! = Sregex_token_iterator ())

    {

        "["]" ;

        ++pos;

    }

    cout << Endl;

    If the last parameter, args, is-1, the matched string is treated as a delimiter

    Split_reg(","); 

    pos = Sregex_token_iterator (Str.begin (), Str.end (), Split_reg,-1);

    while (pos! = Sregex_token_iterator ())

    {

        "["]" ;

        ++pos;

    }

    cout << Endl;

    If the last parameter, args, is a positive number, the first args substring of the matching result is returned

    Split_sub_reg("(\\w*) @(\\w*).  (\\w*) ");

    1);

    while (pos! = Sregex_token_iterator ())

    {

        "["]" ;

        ++pos;

    }

    cout << Endl;

    Match and specify output order

    Extract the date from the following string and convert it to the sequential output of month and day

    std::stringinput("01/02/2003 blahblah 04/23/1999 blahblah 11/13/1981");   

    Re("(\\d{2})/(\\d{2})/(\\d{4})date    

    Year,month, Day

    Begin(Input.begin (), input.  End(), Re, sub_matches), end;  

    To Std::cout

    std::std::"\ n");   

    Std::copy (begin, end, Out_iter);

}

(iv) The regular expression of the boost library regex