std::string all numeric

[salehhamadeh]

bool check_string_numeric(std::string str)
{
    for(int i = 0; i < str.length(); i++)
    {
        if(!( (str.c_str()[i] >= '0') && (str.c_str()[i] <= '9') ) )
        {
            //Not numeric
            return false;
        }
    }
    //numeric
    return true;
}