nullary_indexing.cpp revision 2b8756b6f1de65d3f8bffab45be6c44ceb7411fc 
1#include <Eigen/Core>
2#include <iostream>
3
4using namespace Eigen;
5
6// [functor]
7template<class ArgType, class RowIndexType, class ColIndexType>
8class indexing_functor {
9  const ArgType &m_arg;
10  const RowIndexType &m_rowIndices;
11  const ColIndexType &m_colIndices;
12public:
13  typedef Matrix<typename ArgType::Scalar,
14                 RowIndexType::SizeAtCompileTime,
15                 ColIndexType::SizeAtCompileTime,
16                 ArgType::Flags&RowMajorBit?RowMajor:ColMajor,
17                 RowIndexType::MaxSizeAtCompileTime,
18                 ColIndexType::MaxSizeAtCompileTime> MatrixType;
19
20  indexing_functor(const ArgType& arg, const RowIndexType& row_indices, const ColIndexType& col_indices)
21    : m_arg(arg), m_rowIndices(row_indices), m_colIndices(col_indices)
22  {}
23
24  const typename ArgType::Scalar& operator() (Index row, Index col) const {
25    return m_arg(m_rowIndices[row], m_colIndices[col]);
26  }
27};
28// [functor]
29
30// [function]
31template <class ArgType, class RowIndexType, class ColIndexType>
32CwiseNullaryOp<indexing_functor<ArgType,RowIndexType,ColIndexType>, typename indexing_functor<ArgType,RowIndexType,ColIndexType>::MatrixType>
33indexing(const Eigen::MatrixBase<ArgType>& arg, const RowIndexType& row_indices, const ColIndexType& col_indices)
34{
35  typedef indexing_functor<ArgType,RowIndexType,ColIndexType> Func;
36  typedef typename Func::MatrixType MatrixType;
37  return MatrixType::NullaryExpr(row_indices.size(), col_indices.size(), Func(arg.derived(), row_indices, col_indices));
38}
39// [function]
40
41
42int main()
43{
44  std::cout << "[main1]\n";
45  Eigen::MatrixXi A = Eigen::MatrixXi::Random(4,4);
46  Array3i ri(1,2,1);
47  ArrayXi ci(6); ci << 3,2,1,0,0,2;
48  Eigen::MatrixXi B = indexing(A, ri, ci);
49  std::cout << "A =" << std::endl;
50  std::cout << A << std::endl << std::endl;
51  std::cout << "A([" << ri.transpose() << "], [" << ci.transpose() << "]) =" << std::endl;
52  std::cout << B << std::endl;
53  std::cout << "[main1]\n";
54
55  std::cout << "[main2]\n";
56  B =  indexing(A, ri+1, ci);
57  std::cout << "A(ri+1,ci) =" << std::endl;
58  std::cout << B << std::endl << std::endl;
59#if __cplusplus >= 201103L
60  B =  indexing(A, ArrayXi::LinSpaced(13,0,12).unaryExpr([](int x){return x%4;}), ArrayXi::LinSpaced(4,0,3));
61  std::cout << "A(ArrayXi::LinSpaced(13,0,12).unaryExpr([](int x){return x%4;}), ArrayXi::LinSpaced(4,0,3)) =" << std::endl;
62  std::cout << B << std::endl << std::endl;
63#endif
64  std::cout << "[main2]\n";
65}
66
67