重载operator + C ++时出错

Question

I'm having a problem trying to add two 2D matrices with the overloaded operator+. I've successfully assigned the two matrices to two different arrays.

My errors are:

In function `mathadd::matrices mathadd::operator+(mathadd::matrices&, mathadd::matrices&)':

no matching function for call to `mathadd::matrices::matrices(double&)'

candidates are: mathadd::matrices::matrices(const mathadd::matrices&)

In my int main() {} the main parts of this error are:

matrices sample;
double array1[4][4], array2[4][4], add[4][4];
add[4][4] = array1[4][4] + array2[4][4];

The overloaded operator definition is:

  matrices operator +(matrices& p1, matrices& p2) { double addition[4][4]; for (int y = 0; y < 4; ++y ) { for (int x = 0; x < 4; ++x ) { addition[4][4] = p1.get_array1() + p2.get_array2(); } } matrices sum(addition[4][4]); // This is where the error is. return sum; } 

My class looks like this

class matrices
  {
        public:
               matrices();
               void assignment(double one[4][4], double two[4][4]);
               double get_array1() const {return first_array[4][4];}
               double get_array2() const {return second_array[4][4];} 
               matrices operator +(matrices& p1, matrices& p2);
        private:
                double first_array[4][4], second_array[4][4];
                //Initialized to 0 in constructor.
  };

I don't understand what this error means and I would appreciate any help in understanding what it means and how I can fix it.

Answer 1

addition[4][4] is a double out-of-bounds array access to get the fifth double from the fifth double[] named by addition . Just pass the name addition instead of addition[4][4] in matrices sum(addition[4][4]) .

So it should be

matrices sum(addition);
return sum;

That is only the source of your compiler error. You also have many logic errors in your code, such as the out-of-bounds array access I mentioned earlier, in the inner for -loop. You will have to fix these or else get undefined behavior.

Answer 2

You get an error because your operator + is defined for objects of type matrices , not for 2D arrays of double s. You need to construct matrices before adding them, like this:

First, add a constructor for matrices that takes double[4][4] . Then, change the signature of the operator + to be static , and take a const reference to its parameters:

static matrices operator +(const matrices& p1, const matrices& p2);

Now you can write this:

matrices add = matrices(array1) + matrices(array2);