Converting from a std::string to bool

Question

What is the best way to convert a std::string to bool? I am calling a function that returns either \"0\" or \"1\", and I need a clean solution for turning this into a boole

Answer 1

DavidL's answer is the best, but I find myself wanting to support both forms of boolean input at the same time. So a minor variation on the theme (named after std::stoi):

bool stob(std::string s, bool throw_on_error = true)
{
    auto result = false;    // failure to assert is false

    std::istringstream is(s);
    // first try simple integer conversion
    is >> result;

    if (is.fail())
    {
        // simple integer failed; try boolean
        is.clear();
        is >> std::boolalpha >> result;
    }

    if (is.fail() && throw_on_error)
    {
        throw std::invalid_argument(s.append(" is not convertable to bool"));
    }

    return result;
}

This supports "0", "1", "true", and "false" as valid inputs. Unfortunately, I can't figure out a portable way to also support "TRUE" and "FALSE"

Answer 2

Try this:

bool value;

if(string == "1")
    value = true;
else if(string == "0")
    value = false;