如何創建const boost矩陣？

Question

如何創建常量提升矩陣？

下不工作：

const boost::numeric::ublas::matrix<double> arrayM(1, 3) = { {1.0, 2.0, 3.0} }; 

Answer 1

通常以一個類似於：

typedef boost::numeric::ublas::matrix<double> matrix_type; 

const matrix_type get_matrix(void) 
{ 
    matrix_type result(1, 3); 
    result(0, 0) = 1; 
    result(0, 1) = 2; 
    result(0, 2) = 3; 

    return result; 
} 

const matrix_type arrayM = get_matrix(); 

---

你也可以嘗試這樣的事情（主要是未經測試）：

#include <boost/numeric/ublas/matrix.hpp> 
#include <boost/numeric/ublas/io.hpp> 

template <typename T, typename L = boost::numeric::ublas::row_major, 
      typename A = boost::numeric::ublas::unbounded_array<T> > 
class matrix_builder 
{ 
public: 
    // types 
    typedef boost::numeric::ublas::matrix<T, L, A> matrix_type; 
    typedef typename matrix_type::size_type size_type; 

    // creation 
    matrix_builder(size_type pRows, size_type pColumns) : 
    mMatrix(pRows, pColumns), 
    mRow(0), 
    mColumn(0) 
    {} 

    matrix_builder& operator()(const T& pValue) 
    { 
     mMatrix(mRow, mColumn) = pValue; 
     if (++mColumn == mMatrix.size2()) 
     { 
      mColumn = 0; 
      mRow++; 
     } 

     return *this; 
    } 

    // access 
    operator const matrix_type&(void) const 
    { 
     return mMatrix; 
    } 

private: 
    // non copyable 
    matrix_builder(const matrix_builder&); 
    matrix_builder& operator=(const matrix_builder&); 

    // members 
    matrix_type mMatrix; 
    size_type mRow; 
    size_type mColumn; 
}; 

typedef boost::numeric::ublas::matrix<double> matrix_type; 

static const matrix_type m1 = matrix_builder<double>(3, 1) 
           (1)(2)(3); 

static const matrix_type m2 = matrix_builder<double>(3, 3) 
           (1)(2)(3) 
           (4)(5)(6) 
           (7)(8)(9); 

int main(void) 
{ 
    std::cout << m1 << std::endl; 
    std::cout << m2 << std::endl; 
} 

相同的想法，更通用。還有一點更直觀，可以很好。