Pros:
- it is convenient to type and read numbers this way;
- Ada, Perl, C++, Go and Rust already support that;
- can support thousands as well as lakhs and crores;

Cons:
- standard SQL does not have this support;
- PostgreSQL treat `SELECT 1_000_000` as number one with `_000_000` alias: http://sqlfiddle.com/#!17/0a28f/400
- C++ has `1'000'000` instead of `1_000_000`;

What do you think?

}
        case '0':
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
        case '6':
        case '7':
        case '8':
        case '9':
        {
            
            
            
            
            if (prev_significant_token_type == TokenType::Dot)
            {
                ++pos;
                while (pos < end && isNumericASCII(*pos))
                    ++pos;
            }
            else
            {
                
                bool hex = false;
                if (pos + 2 < end && *pos == '0' && (pos[1] == 'x' || pos[1] == 'b' || pos[1] == 'X' || pos[1] == 'B'))
                {
                    if (pos[1] == 'x' || pos[1] == 'X')
                        hex = true;