Convert a String In C++ To Upper Case

Question

How could one convert a string to upper case. The examples I have found from googling only have to deal with chars.

Answer 1

#include <algorithm>
#include <string>

std::string str = "Hello World";
std::transform(str.begin(), str.end(),str.begin(), ::toupper);

Answer 2

Short solution using C++11 and toupper().

for (auto & c: str) c = toupper(c);

Answer 3

//works for ASCII -- no clear advantage over what is already posted...

std::string toupper(const std::string & s)
{
    std::string ret(s.size(), char());
    for(unsigned int i = 0; i < s.size(); ++i)
        ret[i] = (s[i] <= 'z' && s[i] >= 'a') ? s[i]-('a'-'A') : s[i];
    return ret;
}

Answer 4

typedef std::string::value_type char_t;

char_t up_char( char_t ch )
{
    return std::use_facet< std::ctype< char_t > >( std::locale() ).toupper( ch );
}

std::string toupper( const std::string &src )
{
    std::string result;
    std::transform( src.begin(), src.end(), std::back_inserter( result ), up_char );
    return result;
}

const std::string src  = "test test TEST";

std::cout << toupper( src );

Answer 5

This c++ function always returns the upper case string...

#include <locale> 
#include <string>
using namespace std; 
string toUpper (string str){
    locale loc; 
    string n; 
    for (string::size_type i=0; i<str.length(); ++i)
        n += toupper(str[i], loc);
    return n;
}

Answer 6

As long as you are fine with ASCII-only and you can provide a valid pointer to RW memory, there is a simple and very effective one-liner in C:

void strtoupper(char* str)
{ 
    while (*str) *(str++) = toupper((unsigned char)*str);
}

This is especially good for simple strings like ASCII identifiers which you want to normalize into the same character-case. You can then use the buffer to construct a std:string instance.