DirectSum.hpp

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#ifndef MISC_DIRECTSUM_HPP
#define MISC_DIRECTSUM_HPP

#include <armadillo>
#include <type_traits>

namespace solid
{

template <template <typename> class T1, typename T2>
T1<T2> DirectSum(T1<T2> A, T1<T2> B)
{
    unsigned long int ncA = A.n_cols;
    unsigned long int ncB = B.n_cols;
    unsigned long int nrA = A.n_rows;
    unsigned long int nrB = B.n_rows;

    T1<T2> ret(nrA + nrB, ncA + ncB);

    if constexpr (std::is_same<T1<T2>, arma::Mat<T2>>::value)
        ret.fill(0);
    ret.submat(0, 0, nrA - 1, ncA - 1) = A;
    ret.submat(nrA, ncA, nrA + nrB - 1, ncA + ncB - 1) = B;
    return ret;
}

} // namespace solid

#endif