Question

I want to replace the bitshift bool overload for i/ostream. The current implementation only takes in input strings of “0” or “1” and outputs only “0” or “1”. I want to make a bool overload that considers other sequences such as “t”,”true”,”f”,”false”, etc… Is there anyway to do this, even if its confined to a limited scope? This is the code I want to use:

inline std::ostream& operator << (std::ostream& os, bool b)
{
    return os << ( (b) ? "true" : "false" );
}

inline std::istream& operator >> (std::istream& is, bool& b)
{
    string s;
    is >> s;
    s = Trim(s);

    const char*  true_table[5] = { "t", "T", "true" , "True ", "1" };
    const char* false_table[5] = { "f", "F", "false", "False", "0" };

    for (uint i = 0; i < 5; ++i)
    {
        if (s == true_table[i])
        {
            b = true;
            return is;
        }
    }

    for (uint i = 0; i < 5; ++i)
    {
        if (s == false_table[i])
        {
            b = false;
            return is;
        }
    }

    is.setstate(std::ios::failbit);
    return is;
}

Answer 1

If you’re willing to drop t and f as possibilities you can just use std::boolalpha and std::noboolalpha

from cppreference:

// boolalpha output
std::cout << std::boolalpha 
          << "boolalpha true: " << true << '\n'
          << "boolalpha false: " << false << '\n';
std::cout << std::noboolalpha 
          << "noboolalpha true: " << true << '\n'
          << "noboolalpha false: " << false << '\n';
// booalpha parse
bool b1, b2;
std::istringstream is("true false");
is >> std::boolalpha >> b1 >> b2;
std::cout << '\"' << is.str() << "\" parsed as " << b1 << ' ' << b2 << '\n';

Output:

boolalpha true: true
boolalpha false: false
noboolalpha true: 1
noboolalpha false: 0
"true false" parsed as 1 0