(iv) The regular expression of the boost library regex

Source: Internet
Author: User

(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

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