#100 concat() for sparse vectors

[Michael Meidlinger]

While using the it++ library, I realized there is no concat() functionality for sparse vectors. This would be very helpful in my situation.

[Michael Meidlinger]

Suggestion for implementation: (Warning: I'm new to C++) to include in base/svec.h

template <class T>
Sparse_Vec<T> concat(const Sparse_Vec<T>& v1, const Sparse_Vec<T>& v2)
{
    int vs1 = v1.v_size;
    int vs2 = v2.v_size;
    int ds1 = v1.data_size;
    int ds2 = v2.data_size;
    int us1 = v1.used_size;
    int us2 = v2.used_size;

    // create new vector
    Sparse_Vec<T> temp(vs1+vs2,ds1+ds2);
    // copy data
    copy_vector(us1, v1.data, temp.data);
    copy_vector(us2, v2.data, &temp.data[us1]);
    // adjust indices
    copy_vector(us1, v1.index, temp.index);
    // update used size
    temp.used_size = us1+us2;
    // append indices
    for(int i=0;i<us2;i++){
        temp.index[us1+i] = vs1 + v2.index[i];
    }
    return temp;
}