字符串在C++中降低/降低

#include<iostream>
#include<string>
#include <cctype>

int main() {
    std::string str = "Hello, World!";
    for (char& c : str) {
        c = std::tolower(c);
    }
    std::cout << "Lowercase string: "<< str<< std::endl;
    return 0;
}

Lowercase string: hello, world!