split string by regex in cpp --special case

Question

I want to split this expression

A+ + B

by the "+" in between so that I have A+ and B at the end

Note that the + after A is apart of the first token and I don't want to split it

#include <iostream>
#include <string>
#include <fstream>
#include <sstream>
#include <boost/algorithm/string/regex.hpp>
#include <vector>
using namespace std;

int main()
{
    string expression="A+ + B"; 
    vector <string> resultArray;
    boost::algorithm::split_regex( resultArray, expression,  boost::regex( " + " ));
    for (int i=0; i<resultArray.size();i++){
    cout <<resultArray[i]<< endl ;
    }
return 0;
}

yes the plus with space before and after it

user1876128
– user1876128

2014-01-17 14:44:52 +00:00
Commented Jan 17, 2014 at 14:44 — user1876128
– user1876128, Commented Jan 17, 2014 at 14:44

Sabuj Hassan · Accepted Answer · 2014-01-17 14:45:20Z

1

+ is a regex character and you have to escape it. Not sure how it do in c++ but usually in other languages its done using a backslash(\) like this \+ and, for the space, you can use \s

So assume this will be your splitting regex:

\\s+\\+\\s+

It means: any number of spaces, then a plus, then any number of spaces.

answered Jan 17, 2014 at 14:45

Sabuj Hassan

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John Dibling · Accepted Answer · 2014-01-17 15:26:14Z

0

The + needs to be escaped with \, and furthermore the \ itself needs to be escaped with \ again because this is C++. So:

int main()
{
    string expression="A+ + B"; 
    vector <string> resultArray;
    boost::regex rx(" \\+ ");
    boost::algorithm::split_regex( resultArray, expression, rx);
    for (size_t i=0; i<resultArray.size();i++)
    {   
        cout << "[" << i << "] : " << resultArray[i]<< endl ;
    }   
return 0;
}

Output:

jdibling@hurricane:~/dev/hacks$ ./hacks 
[0] : A+
[1] : B

answered Jan 17, 2014 at 15:26

John Dibling

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