Eric Scöerg - 11 months ago 51

C++ Question

I'd like to read a matrix from cin, using a function, then return matrix back to main.

Here's my code:

**main.cpp**

`#include <iostream>`

#include <windows.h>

#include <vector>

#include "mymath.h"

using namespace std;

int main(){

vector<vector<double>> matrix_read();

Sleep(60000);

return 0;

}

`#pragma once`

#ifndef MYMATH_H

#define MYMATH_H

vector<vector<double>> matrix_read();

#endif

`#include "mymath.h"`

#include <vector>

#include <iostream>

using namespace std;

vector<vector<double>> matrix_read() {

cout << "How big is the quadratic matrix A?\n";

int n;

//row&column size A

cin >> n;

vector<vector<double>> A(n, vector<double>(n));

//fill matrix A

for (int i = 0; i < n; i++) {

for (int j = 0; j < n; j++) {

cin >> A[i][j];

}

}

//control matrix A:

cout << "Please be sure this is the correct Matrix A: \n";

for (int i = 0; i < n; i++) {

for (int j = 0; j < n; j++) {

cout << A[i][j] << " ";

}

cout << endl;

}

return A;

}

for reference:

Return multidimensional vector from function for use in main, how to use correctly?

Error list

The error list implies there's a major mistake. Thank you for your help. Please be gentle, newbie here.

Answer Source

You need to prefix

`vector`

with`std::vector`

in the header, if you did not have`using namespace std;`

before the include directive. Anyway, it's good practice to have`std::`

in the header.In main, it should be

`int main(){ vector<vector<double>> matrix = matrix_read(); Sleep(60000); return 0; }`

i.e. you set the object `matrix`

to the return value of the function. Otherwise, you would define another prototype for `matrix_read`

in the main function.