Question

我的类是由向量向量组成的矩阵，我的构造函数似乎有问题：

Matric<int> m(5,5); Matrix<int> n=(m);

当我尝试使用复制构造函数时，代码将无法编译，与In file included from /usr/lib/gcc/x86_64-pc-cygwin/5.4.0/include/c++/vector:60:0, from /cppex3/ex3/Matrix.hpp:8, from /cppex3/ex3/Tester.cpp:6: /usr/lib/gcc/x86_64-pc-cygwin/5.4.0/include/c++/bits/stl_algobase.h: In instantiation of '_OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove = false; _II = const std::vector<int, std::allocator<int> >*; _OI = std::vector<std::vector<int, std::allocator<int> >, std::allocator<std::vector<int, std::allocator<int> > > >]': /usr/lib/gcc/x86_64-pc-cygwin/5.4.0/include/c++/bits/stl_algobase.h:438:45: required from '_OI std::__copy_move_a2(_II, _II, _OI) [with bool _IsMove = false; _II = __gnu_cxx::__normal_iterator<const std::vector<int, std::allocator<int> >*, std::vector<std::vector<int, std::allocator<int> >, std::allocator<std::vector<int, std::allocator<int> > > > >; _OI = std::vector<std::vector<int, std::allocator<int> >, std::allocator<std::vector<int, std::allocator<int> > > >]' /usr/lib/gcc/x86_64-pc-cygwin/5.4.0/include/c++/bits/stl_algobase.h:471:8: required from '_OI std::copy(_II, _II, _OI) [with _II = __gnu_cxx::__normal_iterator<const std::vector<int, std::allocator<int> >*, std::vector<std::vector<int, std::allocator<int> >, std::allocator<std::vector<int, std::allocator<int> > > > >; _OI = std::vector<std::vector<int, std::allocator<int> >, std::allocator<std::vector<int, std::allocator<int> > > >]' /ex3/Matrix.hpp:42:13: required from 'Matrix<T>::Matrix(const Matrix<T>&) [with T = int]' /ex3/Tester.cpp:25:20: required from here /usr/lib/gcc/x86_64-pc-cygwin/5.4.0/include/c++/bits/stl_algobase.h:394:57: error: no type named 'value_type' in '[01mstruct std::iterator_traits<std::vector<std::vector<int, std::allocator<int> >, std::allocator<std::vector<int, std::allocator<int> > > > >' typedef typename iterator_traits<_OI>::value_type _ValueTypeO; ^ /usr/lib/gcc/x86_64-pc-cygwin/5.4.0/include/c++/bits/stl_algobase.h:399:9: error: no type named 'value_type' in 'struct std::iterator_traits<std::vector<std::vector<int, std::allocator<int> >, std::allocator<std::vector<int, std::allocator<int> > > > >' && __are_same<_ValueTypeI, _ValueTypeO>::__value); ^中一样，因为：

https://pbs.twimg.com/profile_images/1580483969/parisjs_transparent.png

我怀疑我对_matrix成员的初始化是不正确的，但我不确定。它也可以通过std :: copy但语法似乎是正确的。

Answer 1

尝试

copy(other._matrix[i].begin(), other._matrix[i].end(), 
     std::back_inserter(_matrix[i]));

或

Matrix (const Matrix<T> &other)
   : _rows{other._rows}, _cols{other._cols}, _matrix{other._matrix}
 {
 }

Answer 2

尝试使用此代码，它可以正常工作

替换

copy(other._matrix[i].begin(), other._matrix[i].end(), _matrix[i]);

<强> 与

copy(other._matrix[i].begin(), other._matrix[i].end(), _matrix[i].begin());

以下是完整的代码。

#include <vector>
#include <exception>
#include <iostream>

using namespace std;

template<class T>
class Matrix
{
private:

    unsigned int _rows;
    unsigned int _cols;
    vector <vector<T> > _matrix;

public:

    Matrix () : _rows(1), _cols(1),
                _matrix(1,vector<T>(1))
    {
        cout << "ctor" << endl;
    }

    Matrix (unsigned int rows, unsigned int cols) : _rows(rows), _cols(cols)
    {
        _matrix=vector< vector<T> >(rows,vector<T>(cols));
    }


    Matrix (const Matrix<T> &other)
     : _rows{other._rows}, _cols{other._cols}, _matrix{other._matrix}
    {
        for(int i = 0; i < _rows; i++)
        {
            std::copy(other._matrix[i].begin(), other._matrix[i].end(), _matrix[i].begin());
        }
    }

};


int main(int argc, char const *argv[])
{
    Matrix<int> m(5,5);
    Matrix<int> n1(m);
    Matrix<int> n2(m);
    return 0;
}

另外

Matrix (const Matrix<T> &other) :Matrix(other._rows, other._cols);

将其替换为

Matrix (const Matrix<T> &other) {
    Matrix(other._rows, other._cols);
...

c ++ - 模板类的复制构造函数

2 个答案: