How to Convert a C++ String to Uppercase
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 the std namespace (accessed with std::toupper) which has multiple overloads and thus cannot be simply referenced with a name only. You … Read more