28 lines
673 B
C++
28 lines
673 B
C++
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#include <Eigen/Core>
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#include <iostream>
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using namespace Eigen;
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using namespace std;
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template<typename Derived>
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Eigen::VectorBlock<Derived, 2>
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firstTwo(MatrixBase<Derived>& v)
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{
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return Eigen::VectorBlock<Derived, 2>(v.derived(), 0);
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}
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template<typename Derived>
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const Eigen::VectorBlock<const Derived, 2>
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firstTwo(const MatrixBase<Derived>& v)
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{
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return Eigen::VectorBlock<const Derived, 2>(v.derived(), 0);
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}
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int main(int, char**)
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{
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Matrix<int,1,6> v; v << 1,2,3,4,5,6;
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cout << firstTwo(4*v) << endl; // calls the const version
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firstTwo(v) *= 2; // calls the non-const version
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cout << "Now the vector v is:" << endl << v << endl;
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return 0;
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}
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