Got problem converting string to upper case letters

Question

Using following console application i am converting each string to uppercase letters. But string value in output remains unchanged. what I am doing wrong here. Also any help on doing this efficiently would be appreciated.Thanks for your help.

int main()
{    

    vector<string> svec, svec_out;
    string word;
    int run;

    cout << "Press 0 to quit giving input string" << endl;

    while(1)
    {
        cin >> word;
        svec.push_back(word);

        cin >> run;
        if (!run)
            break;
    }

    cout << "converting to upper case... " << endl;

    int i;
    for (i = 0; i!=svec.size(); ++i)
    {
        word = svec[i];
        for (string::size_type j=0; j < word.size(); ++j)
        {
            toupper(word[j]);
        }

        svec_out.push_back(word);
    }


    for ( i = 0; i<svec_out.size(); i++)
        cout << svec_out[i] << endl;

    return 0;
}

Answer 1

toupper will return the uppercase value instead of modifying the value in-place. As such your code should read:

word[j] = toupper(word[j]);

Answer 2

A simple reminder (more than an answer): calling ::toupper with a type char is undefined behavior (even if most implementations try to make it work most of the time). The global ::toupper function requires an int in input, and that int must be in the range [0, UCHAR_MAX] or be equal to EOF (usually -1). If plain char is signed (the most frequent case), you will end up calling ::toupper with negative values.

Answer 3

kinda outdated but you can change:

for (string::size_type j=0; j < word.size(); ++j)
    {
        toupper(word[j]);
    }

to:

for (auto &j : word) // for every j in word (note j is a reference)
    j=toupper(j);   // replace that j with it's uppercase

Just learned this stuff from C++ Primer - Part I - chapter 3

Answer 4

Ok I got the problem. miss the toupper() method's return value

Answer 5

I think you should assign the toUpper value to your word

word[j] = toupper(word[j]);

That should do.

Answer 6

Use std::transform as:

#include <iostream>
#include <string>
#include <algorithm>
#include <iterator>
#include <cctype>

int main() {
   std::string s="nawaz";
   std::string S;
   std::transform(s.begin(),s.end(), std::back_inserter(S), ::toupper);
   std::cout << S ;
}

Output:

NAWAZ

Online demo: http://ideone.com/WtbTI

Answer 7

#include <algorithm>
using namespace std;
transform(svec[i].begin(), svec[i].end(), svec[i].begin(), toupper);

Answer 8

I bid for the shortest bit of code:

 #include <boost/algorithm/string.hpp>

 boost::to_upper(svec);

You can find many more in Boost String Algorithm , [to_upper][2] modifies the string in place and also features a to_upper_copy cousin, which returns a (transformed) copy and leaves the original string untouched.