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