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27 lines
722 B
C++
27 lines
722 B
C++
#include <Eigen/Core>
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USING_PART_OF_NAMESPACE_EIGEN
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using namespace std;
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template<typename Derived>
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Eigen::Block<Derived,1,Derived::ColsAtCompileTime>
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firstRow(MatrixBase<Derived>& m)
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{
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return Eigen::Block<Derived,1,Derived::ColsAtCompileTime>(m.asArg(), 0);
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}
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template<typename Derived>
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const Eigen::Block<Derived,1,Derived::ColsAtCompileTime>
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firstRow(const MatrixBase<Derived>& m)
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{
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return Eigen::Block<Derived,1,Derived::ColsAtCompileTime>(m.asArg(), 0);
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}
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int main(int, char**)
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{
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Matrix4d m = Matrix4d::identity();
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cout << firstRow(2*m) << endl; // calls the const version
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firstRow(m) *= 5; // calls the non-const version
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cout << "Now the matrix m is:" << endl << m << endl;
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return 0;
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}
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