How to make a test with arrays using asserts? - c++

Question

I'm trying to write a test for a program that adds the product of matrices A and X to the matrix Y.
But I got the error:
"Identifier is required"
I couldn't solve or find a solution to this problem, so I ask for help here.
At first, I thought that the problem is that I compare it with the wrong array. Then I tried to pass other arguments. Dismembered my code into several functions. But still, nothing happened.
#include<iostream>
#include<cassert>
using namespace std;
void axpy(int n, int m, int k, int **A, int **X, int **Y)
{
int i, j, q;
for (i = 0; i < n; i++)
{
for (j = 0; j < m; j++)
{
for (q = 0; q < k; q++)
{
Y[i][j] += A[i][q] * X[q][j];
}
}
}
cout << "Product of matrices\n";
for (i = 0; i < n; i++)
{
for (j = 0; j < m; j++)
cout << Y[i][j] << " ";
cout << "\n";
}
}
void TestAxpy()
{
int P[2][2] = { {13,11},{27,21} };
assert(axpy(2,2,2,[1,2][3,4],[4,3][2,1],[5,6][7,8]) == P);
}
int main()
{
int n, m, k, i, j, q;
cout << "Enter number of rows of matrix X and columns of matrix A: ";
cin >> k;
cout << "Enter number of rows of matrix A and Y: ";
cin >> n;
cout << "Enter number of columns of matrix X and Y: ";
cin >> m;
int **A = new int *[k];
for (i = 0; i < k; i++)
A[i] = new int[n];
int **X = new int *[m];
for (i = 0; i < m; i++)
X[i] = new int[k];
int **Y = new int *[m];
for (i = 0; i < m; i++)
Y[i] = new int[n];
cout << "Enter elements of matrix A: ";
for (i = 0; i < n; i++)
for (j = 0; j < k; j++)
cin >> A[i][j];
cout << "Enter elements of matrix X: ";
for (i = 0; i < k; i++)
for (j = 0; j < m; j++)
cin >> X[i][j];
cout << "Enter elements of matrix Y: ";
for (i = 0; i < n; i++)
for (j = 0; j < m; j++)
cin >> Y[i][j];
axpy(n, m, k, A, X, Y);
TestAxpy();
system("pause");
return 0;
}
I wanted to get a 2x2 matrix with the results of [13, 11] [27 21]. The input I used such as:
Enter number of rows of matrix X and columns of matrix A: 2
Enter number of rows of matrix A and Y: 2
Enter number of columns of matrix X and Y: 2
Enter elements of matrix A: 1 2 3 4
Enter elements of matrix X: 4 3 2 1
Enter elements of matrix Y: 5 6 7 8

Answer 1

This seems like a mix of C and C++. In C++ it is rare you need to use raw "C" arrays, almost always std::vector<> or std::array<> will be a better choice. There is also matrix in the boost library which will store exactly what you need.
In terms of your specific code there are two issues:
Pointers to pointers (**) are no the same thing as two dimension arrays. They are a two-layer indirection. The first are pointers to locations in memory that store the second layer in memory. See below for how it would need to work to be able to call axpy. Again would strongly recommend looking at std::vector or boost libraries.
The "==" operator won't work that way for C arrays. You need to specify how you want the comparison to happen. As written it will at best just compare memory address, but more likely will produce an error.
void TestAxpy()
{
int P[2][2] = { {13,11},{27,21} };
int A1[2] = {1,2};
int A2[2] = {3,4};
int* A[2] = { A1, A2 };
int X1[2] = {4,3};
int X2[2] = {2,1};
int *X[2] = { X1, X2 };
int Y1[2];
int Y2[2];
int *Y[2] = {Y1, Y2 };
axpy(2,2,2,A,X,Y);
//assert(Y == P); //C++ doesn't know how to do this.
}