and this is probably something similar to how isxdigit or isdigit works. you only need one or two li

and this is probably something similar to how isxdigit or isdigit works. you only need one or two lines

bool is_digit(char c)
{
    return c >= '0' && c <= '9';
}

bool is_digit(char c)
{
    return c >= '0' && c <= '9';
}

bool is_digit(char c)
{
    return c >= '0' && c <= '9';
}

bool is_digit(char c)
{
    return c >= '0' && c <= '9';
}