Function distance_squared

dlib/svm/sparse_vector.h:22–70

    template <typename T, typename U>
    typename T::value_type::second_type distance_squared (
        const T& a,
        const U& b
    )
    {
        typedef typename T::value_type::second_type scalar_type;
        typedef typename U::value_type::second_type scalar_typeU;
        // Both T and U must contain the same kinds of elements
        COMPILE_TIME_ASSERT((is_same_type<scalar_type, scalar_typeU>::value));

        typename T::const_iterator ai = a.begin();
        typename U::const_iterator bi = b.begin();

        scalar_type sum = 0, temp = 0;
        while (ai != a.end() && bi != b.end())
        {
            if (ai->first == bi->first)
            {
                temp = ai->second - bi->second;
                ++ai;
                ++bi;
            }
            else if (ai->first < bi->first)
            {
                temp = ai->second;
                ++ai;
            }
            else 
            {
                temp = bi->second;
                ++bi;
            }

            sum += temp*temp;
        }

        while (ai != a.end())
        {
            sum += ai->second*ai->second;
            ++ai;
        }
        while (bi != b.end())
        {
            sum += bi->second*bi->second;
            ++bi;
        }

        return sum;
    }

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