struct writer
    {
        template <typename T> T &operator<<(T x)
        {
            static_assert(is_integral<T>::value, "only interger!");
            int sta[50];
            int tp = 0;
            do
            {
                sta[tp++] = x % 10;x /= 10;
            } while (x);
            while (tp) putchar(sta[--tp] + '0');
        }
    } write;

调用

int x = 48;
write << x;