How to Convert a C++ String to Uppercase
Boost string algorithms:
#include <boost/algorithm/string.hpp>
#include <string>
std::string str = "Hello World";
boost::to_upper(str);
std::string newstr = boost::to_upper_copy("Hello World");
Convert a String In C++ To Upper Case
Try this small program, straight from C++ reference
#include <iostream>
#include <algorithm>
#include <string>
#include <functional>
#include <cctype>
using namespace std;
int main()
{
string s;
cin >> s;
std::transform(s.begin(), s.end(), s.begin(), std::ptr_fun<int, int>(std::toupper));
cout << s;
return 0;
}
Live demo
You need to put a double colon before toupper
:
transform(input.begin(), input.end(), input.begin(), ::toupper);
Explanation:
There are two different toupper
functions:
toupper
in the global namespace (accessed with::toupper
), which comes from C.toupper
in thestd
namespace (accessed withstd::toupper
) which has multiple overloads and thus cannot be simply referenced with a name only. You have to explicitly cast it to a specific function signature in order to be referenced, but the code for getting a function pointer looks ugly:static_cast<int (*)(int)>(&std::toupper)
Since you're using namespace std
, when writing toupper
, 2. hides 1. and is thus chosen, according to name resolution rules.