Binary search variants

gistfile1.cpp

    bool contains(const T& value)
    {
#if 0 // variant 0
        return std::binary_search(values.begin(), values.end(), value);
#elif 0 // variant 1
        size_t l = 0, r = values.size();
        while (l < r) {
            size_t x = (l + r) >> 1;
            if (values[x] < value)
                l = x + 1;
            else if (values[x] > value)
                r = x;
            else
                return true;
        }

        return false;
#else // variant 2
        const T* base = &values[0]; // grr ignore values.size() == 0 case here.
        size_t n = values.size();
        while (n) {
            size_t x = n >> 1;
            if (base[x] < value) {
                base += x + 1;
                n -= x + 1;
            } else if (base[x] > value)
                n = x;
            else
                return true;
        }

        return false;
#endif
    }