1 namespace Eigen { 2 3 /** \page TopicCustomizing_Plugins Extending MatrixBase (and other classes) 4 5 In this section we will see how to add custom methods to MatrixBase. Since all expressions and matrix types inherit MatrixBase, adding a method to MatrixBase make it immediately available to all expressions ! A typical use case is, for instance, to make Eigen compatible with another API. 6 7 You certainly know that in C++ it is not possible to add methods to an existing class. So how that's possible ? Here the trick is to include in the declaration of MatrixBase a file defined by the preprocessor token \c EIGEN_MATRIXBASE_PLUGIN: 8 \code 9 class MatrixBase { 10 // ... 11 #ifdef EIGEN_MATRIXBASE_PLUGIN 12 #include EIGEN_MATRIXBASE_PLUGIN 13 #endif 14 }; 15 \endcode 16 Therefore to extend MatrixBase with your own methods you just have to create a file with your method declaration and define EIGEN_MATRIXBASE_PLUGIN before you include any Eigen's header file. 17 18 You can extend many of the other classes used in Eigen by defining similarly named preprocessor symbols. For instance, define \c EIGEN_ARRAYBASE_PLUGIN if you want to extend the ArrayBase class. A full list of classes that can be extended in this way and the corresponding preprocessor symbols can be found on our page \ref TopicPreprocessorDirectives. 19 20 Here is an example of an extension file for adding methods to MatrixBase: \n 21 \b MatrixBaseAddons.h 22 \code 23 inline Scalar at(uint i, uint j) const { return this->operator()(i,j); } 24 inline Scalar& at(uint i, uint j) { return this->operator()(i,j); } 25 inline Scalar at(uint i) const { return this->operator[](i); } 26 inline Scalar& at(uint i) { return this->operator[](i); } 27 28 inline RealScalar squaredLength() const { return squaredNorm(); } 29 inline RealScalar length() const { return norm(); } 30 inline RealScalar invLength(void) const { return fast_inv_sqrt(squaredNorm()); } 31 32 template<typename OtherDerived> 33 inline Scalar squaredDistanceTo(const MatrixBase<OtherDerived>& other) const 34 { return (derived() - other.derived()).squaredNorm(); } 35 36 template<typename OtherDerived> 37 inline RealScalar distanceTo(const MatrixBase<OtherDerived>& other) const 38 { return internal::sqrt(derived().squaredDistanceTo(other)); } 39 40 inline void scaleTo(RealScalar l) { RealScalar vl = norm(); if (vl>1e-9) derived() *= (l/vl); } 41 42 inline Transpose<Derived> transposed() {return this->transpose();} 43 inline const Transpose<Derived> transposed() const {return this->transpose();} 44 45 inline uint minComponentId(void) const { int i; this->minCoeff(&i); return i; } 46 inline uint maxComponentId(void) const { int i; this->maxCoeff(&i); return i; } 47 48 template<typename OtherDerived> 49 void makeFloor(const MatrixBase<OtherDerived>& other) { derived() = derived().cwiseMin(other.derived()); } 50 template<typename OtherDerived> 51 void makeCeil(const MatrixBase<OtherDerived>& other) { derived() = derived().cwiseMax(other.derived()); } 52 53 const CwiseBinaryOp<internal::scalar_sum_op<Scalar>, const Derived, const ConstantReturnType> 54 operator+(const Scalar& scalar) const 55 { return CwiseBinaryOp<internal::scalar_sum_op<Scalar>, const Derived, const ConstantReturnType>(derived(), Constant(rows(),cols(),scalar)); } 56 57 friend const CwiseBinaryOp<internal::scalar_sum_op<Scalar>, const ConstantReturnType, Derived> 58 operator+(const Scalar& scalar, const MatrixBase<Derived>& mat) 59 { return CwiseBinaryOp<internal::scalar_sum_op<Scalar>, const ConstantReturnType, Derived>(Constant(rows(),cols(),scalar), mat.derived()); } 60 \endcode 61 62 Then one can the following declaration in the config.h or whatever prerequisites header file of his project: 63 \code 64 #define EIGEN_MATRIXBASE_PLUGIN "MatrixBaseAddons.h" 65 \endcode 66 67 */ 68 69 } 70
