二进制“ [”：找不到使用“初始化列表”类型的右侧操作数的运算符（或者没有可接受的转换）

Question

I get an error when trying to compile my code which says:

error C2679: binary '[': no operator found which takes a right-hand operand of type 'initializer list' (or there is no acceptable conversion). 
note: could be 'double &Matrix<double>::operator [](const std::array<int,2> &)'. 
note: while trying to match the argument list '(Matrix<double>, initializer list)'. 

I don't understand what I am doing wrong. So my question is what's wrong and how to fix it. Also, the assignment is to use

Matrix<double> M(10, 20);
M[{0, 0}] = 1.0; // set value at row 0, column 0 to 1.0

So this part I can't change.

#include "stdafx.h"
#include <iostream>
#include <initializer_list>
#include <memory>
#include <string>
#include <map>


//Matrix Class
template<typename T>
class Matrix {
private:
    int rows;
    int columns;
public:
    std::map< std::array<int, 2>, T > data;
    //Constructor
    Matrix() {
        rows = 0;
        columns = 0;
    }

    Matrix(int rows, int columns)
        : rows(rows), columns(columns)
    {
        //std::clog << "Matrix(int rows, int columns) called" << std::endl;
    }


    //Destructor
    ~Matrix()
    {
        data.clear();
        rows = 0;
        columns = 0;
    }


    T& operator[](const std::array<int, 2>& a) {
        return data[a];
    }
};


int main()
{
    Matrix<double> M(10, 20);
    M[{0, 0}] = 1.0; // set value at row 0, column 0 to 1.0
    //M[{1, 2}] = 2.0; // set value at row 1, column 2 to 2.0


    std::cout << " Finished!" << M[{0, 0}] << std::endl;


    return 0;
}

Answer 1

At the top of the file, after #include "stdafx.h" put

#include <array>

Alternately, you could put that line into the file stdafx.h .

In general, whenever you see an error message saying that something is missing, see if all necessary include-files are present. The message might be "no operator found", "undefined class", or "incomplete type" or something else.