C++ - Errors met while designing a Matrix class

[slizorn]

Hi guys,
well i am learning c++ on my own..
i am studying it by refering to the book and doin its exercises.
well i need help sorting out the errors.. and i am not sure wat destructors and constructors are.. plus i am coding using Visual C++ 2008 express edition..
this program needs me to input a matrix from a file..
the file called matrix1.txt is as follows:
<matrix>
rows = 2
cols = 2

1 2
2 4
</matrix>
so we are meant to input the data from the file into the matrix and carry out the operations..

the code is as follows for Matrix.h

[slizorn]

#pragma once
 
class Matrix
{
public:
    Matrix(void);
    ~Matrix(void);
    void readMatrixFile(string FILENAME);
    void addMatrix(Matrix m1, Matrix m3);
    void displayMatrix();
    void transposeMatrix();
    void multiplyMatrices(Matrix m2, Matrix m3);
 
private:
    int row;
    int col;
    double m[][];
};
 
 

the code for Matrix.cpp is as follows

#include <iostream>
#include <fstream>
#include <string>
#include "Matrix.h"
using namespace std;
 
 
Matrix::Matrix(void)
{
}
 
 
Matrix::~Matrix(void)
{
}
 
 
Matrix::readMatrixFile(string FILENAME)
{
    const string filename(FILENAME);
    ifstream file(filename.c_str());
    string line;
    if (getline(file, line) && line == "<matrix>")
    {
        if (file >> line /* "rows" */ && file >> line /* "=" */ && file >> row && getline(file,line) /* ; */)
        {
            if (file >> line /* "cols" */ && file >> line /* "=" */ && file >> col && getline(file,line) /* ; */)
            {
                for (int r = 0; r < row; r++)
                {
                    for (int c = 0; c < col; c++)
                    {
                        int value;
                        if (file >> value)
                        {
                            m[r][c] = value;
                        }
                    }
                    cout << endl;
                }
            }
        }
    }
}
 
 
Matrix::addMatrix(Matrix m1, Matrix m3) // needs some modification...
{
    for(int a = 0; a < row; a++)
    {
        for(int b = 0; b < col; b++)
        {
            m3[a][b]=(m1[a][b] + m2[a][b]);
        }
    }
}
 
 
Matrix::displayMatrix()
{
    for(int i = 0; i < row; i++)
    {
        cout << "| ";
        for (int j = 0; j < col; j++)
        {
            cout << m3[i][j] << " ";
        }
        cout << "|" << endl;
    }
}
 
 
Matrix::transposeMatrix()
{
    for(int k = 0; k < row; k++)
    {
        for(int j = 0; j < col; j++)
        {
            int save[2][2];
            save[k][j] = m1[k][j];
            m3[k][j] = m1[j][k];
            m3[j][k] = save[k][j];
        }
    }
}
 
 
Matrix::multiplyMatrices(Matrix m2, Matrix m3) // needs soem modification like addMatrix
{
    if(m1.col != m2.row)
    {
        cout << "These two matrices cannot be multiplied!!!" << endl;
    }
    else
    {
        for(int i = 0; i < m1.row; i++)
        {
            for(int j = 0; j < m2.col; j++)
            {
                for(int k = 0; k < m2.row; k++)
                {
                    m3[i][j] = m3[i][j] + m1[i][k] * m2[k][j];
                }
            }
        }
    }
}
 

and the code for exercise2.cpp is as follows

#include <iostream>
#include <fstream>
#include <string>
#include "Matrix.h"
using namespace std;
 
 
int main(int argc, char* argv[])
{
    Matrix m1, m2 ,m3;
    char theOption;
    string filename1, filename2;
 
    while(theOption != '5')
    {
        cout << "Please choose one of the following options from the menu below:" << endl;
        cout << "---------------------------------------------------------------" << endl;
        cout << "(1) Add two matrices" << endl;
        cout << "(2) Multiply two matrices" << endl;
        cout << "(3) Take transpose of a matrix" << endl;
        cout << "(4) Display a matrix" << endl;
        cout << "(5) Exit" << endl;
        cout << "---------------------------------------------------------------" << endl;
        cin >> theOption;
 
        switch(theOption)
        {
            case '1':
                cout << "You have chosen option 1!: Add two matices!" << endl;
                cout << "Please enter the two filenames that contain the two input matrices respectively!" << endl;
                cout << "Enter name of 1st file" << endl;
                cin >> filename1;
                cout << "Enter name of 2nd file" << endl;
                cin >> filename2;
                m1.readMatrixFile(filename1);
                m2.readMatrixFile(filename2);
                m2.addMatrix(m1, m3);
                cout << "The two matrices have been added together." << endl;
                cout << "Select (4): Display a matrix to view it." << endl << endl;
                break;
 
            case '2':
                cout << "You have chosen option 2!: Multiply two matices!" << endl;
                cout << "Please enter the two filenames that contain the two input matrices respectively!" << endl;
                cout << "Enter name of 1st file" << endl;
                cin >> filename1;
                cout << "Enter name of 2nd file" << endl;
                cin >> filename2;
                m1.readMatrixFile(filename1);
                m2.readMatrixFile(filename2);
                m1.multiplyMatrices(m2, m3);
                cout << "The two matrices have been multiplied with each other." << endl;
                cout << "Select (4): Display a matrix to view it." << endl << endl;
                break;
 
            case '3':
                cout << "You have chosen option 3!: Transpose a matrix!" << endl;
                cout << "Please enter the filename that contains the matrix to be transposed!" << endl;
                cout << "Enter name of file" << endl;
                cin >> filename1;
                m1.readMatrixFile(filename1);
                m1.transposeMatrix();
                cout << "The matrix has been transposed." << endl;
                cout << "Select (4): Display a matrix to view it." << endl << endl;
                break;
 
            case '4':
                cout << "You have chosen option 4!: Display a matix!" << endl;
                cout << "Please enter the option 1, 2 or 3 to display the respective matrices!" << endl;
                cin >> whichMatrixToDisplay;
                displayMatrix();
                cout << endl;
                break;
 
            case '5':
                cout << "You have chosen the option to Quit. Goodbye!" << endl;
                break;
 
            default:
                cout << " Sorry the option chosen is invalid. Please enter a valid option!" << endl << endl;
                break;
        }
    }
 
    return 0;
}
 

what is wrong with my program?
thanks in advance.. :D

[arnaudk]

Why do you ask? What happened when you tried to compile and run your code?
Please enclose your code in [i][code=cpp[/i]] ... [/code] tags.

[slizorn]

hi i got lots of errors.
i tried for a few hours to reduce them..
i managed to bring it down from abt 120 errors to 43 errors..
and i tried my best to correct each error..
but looks like i need more experience or help before i can fix them
could u please help me spot the errors?
and teach me how to use the destructos and constructors?
thanks

[newb16]

hi i got lots of errors.
i tried for a few hours to reduce them..
i managed to bring it down from abt 120 errors to 43 errors..
and i tried my best to correct each error..
but looks like i need more experience or help before i can fix them

Is there anything more difficult than missed declaration?

just a few
1) Ewe never allocate memory for m[][], it will crash on first run.
2) in multiplymatrix there is no m1 variable in scope, and m3 elements are left unitialized before ewe add values to them.

eta-47: error: ISO C++ forbids declaration of `readMatrixFile ' with no
type
- so what? add void in front of as in class declaration

::transposeMatr ix()
int save[2][2];
totaly wrong - use double as temp and I eve don't understand how is it supposed to work
m3 is not defined as well

error: no match for 'operator[]' in 'm3[a]'
Yes. Use m3.m[a] instead - from class methods ewe can access private members of classes of your type.

[slizorn]

[quote=newb16][quote=slizorn]hi i got lots of errors.
i tried for a few hours to reduce them..
i managed to bring it down from abt 120 errors to 43 errors..
and i tried my best to correct each error..
but looks like i need more experience or help before i can fix them

Is there anything more difficult than missed declaration?

just a few
1) Ewe never allocate memory for m[][], it will crash on first run.
2) in multiplymatrix there is no m1 variable in scope, and m3 elements are left unitialized before ewe add values to them.

yea about the allocating memory for the m[][]... how do i do it?
i have a rough idea that i got to use new and delete or somethin like that..
but not sure how...
could ya gimme an example for the case where the max size of the matrix is say 10 by 10?
and the thing with (2).. i want to be able to do m1.multiplyMatr ix(m2, m3);
but i get wat u mean but how am i to do it by initialize the m3 elements?

thanks

[newb16]

yea about the allocating memory for the m[][]... how do i do it?

like m=new (double*)[10]; for(i...) m[i]=new double[10];
and... for(i...) delete[] m[i]; delete[] m;

and the thing with (2).. i want to be able to do m1.multiplyMatr ix(m2, m3);
but i get wat u mean but how am i to do it by initialize the m3 elements?
thanks

You need to set each element of m3 to 0 before addition - i.e. before the innermost loop.

[slizorn]

like m=new (double*)[10]; for(i...) m[i]=new double[10];
and... for(i...) delete[] m[i]; delete[] m;


You need to set each element of m3 to 0 before addition - i.e. before the innermost loop.

errm when i did wat u said for the 1st thing.. i jusut get abt 60 more errors... i dun think that is solving the problem.. if u want i can send u the files.. i cant attach it to this forum for some reason..

thanks

[newb16]

I do not sly neponyal nothing. gugltransleyt some hnyu extradite apologize. Send-a ... in profile button pm - sends nivapros.