Reading a matrix created using an operator - c++

Question

Hello stackoverflow community. I need some help with a bit of code (I am a new to C++ so be gentle). I am trying to use operator() to create a matrix, store data from an input file, then write to an output file. The below code has been simplified a bit. The header file is as follows:
//Data Header File
#ifndef Data_h
#define Data_h
#include <iostream>
using namespace std;
class Data
{
private:
int d_elems;
int rows_, cols_;
int dataRows;
int *p;
public:
//Constructor
femData();
femData(int Row, int Col);
//Copy Constructor
//femData(const int d_elems);
//Destructor
virtual ~femData();
//Operator
int& operator() (int Rows, int Cols);
//Functions
void readData(istream &inp); //Read Data from Input File
void writeData(ostream &out); //Write Data from Output File
};
#endif
Any my .cpp file:
//.cpp file
#include "stdafx.h"
#include "Data.h"
#include <fstream>
#include <string>
#include <iostream>
#include <iomanip>
using namespace std;
Data::Data() {} //Blanket Constructor
Data::Data(int Row, int Col) //Matrix Constructor
: rows_ (Row), cols_ (Col)
{
if (Row == 0 || Col == 0)
{
cout << "\nMatrix is Zero..." << endl;
system("pause");
exit(0);
}
p = new int[Row * Col];
}
int& Data::operator()(int Rows, int Cols) //Operator for Matrix
{
if (Rows >= rows_ || Cols >= cols_)
{
cout << "\nMatrix subscript out of bounds\n";
system("pause");
exit(0);
}
return p[cols_ * Rows + Cols];
}
Data::~Data() { /*delete[] p;*/} //Destructor
void Data::readData(istream &inp)
{
inp >> dataRows;
int e_id;
//Data (dataRows, 10); //How would I call this constructor?
rows_ = dataRows;
cols_ = 10;
for (int i = 0; i < dataRows; i++)
{
inp >> e_id;
if ((e_id - 1) != i)
{
cout << "\nError Reading Data..." << endl;
cout << "Program Will End\n!" << endl;
system("pause");
exit(0);
}
(*this)(i, 0) = d_eid;
for (int j = 1; j < 10; j++)
{
inp >> (*this)(i, j);
}
}
void femData::writeData(ostream & out)
{
//Output Info
out << setfill('-') << setw(90) << "-" << endl;
out << setfill(' ') << setw(34) << " Matrix Information " << endl;
out << setfill('-') << setw(90) << "-" << "\n\n" << endl;
out << setfill(' ');
out << setw(10) << "ID";
out << setw(10) << "Data 1";
out << setw(10) << "Data 2";
out << setw(10) << "Data 3";
out << setw(10) << "Data 4";
out << setw(10) << "Data 5";
out << setw(10) << "Data 6";
out << setw(10) << "Data 7";
out << setw(10) << "Data 8" << endl;
for (int i = 0; i < dataRows; i++)
{
out << setw(7) << ((p + i) + 0);
out << setw(10) << ((p + i) + 1);
out << setw(10) << ((p + i) + 2);
out << setw(10) << ((p + i) + 3);
out << setw(10) << ((p + i) + 4);
out << setw(10) << ((p + i) + 5);
out << setw(10) << ((p + i) + 6);
out << setw(10) << ((p + i) + 7);
out << setw(10) << ((p + i) + 8) << endl;
//Note ((p + i) + 8) is omitted
}
}
The issue I am having is with the output. When the WriteData function is called, it writes to an output file, but does not write the data it read. Instead all that is written is {0 1 2 3 4 5 6 7 8} {1 2 3 4 5 6 7 8 9} {etc.} where {is used here to denote different rows}
Additionally, if I try to output d_elems(i,0) instead of ((d_elems + i) + 0) the compiler tells me I need a pointer to function type.
Any help would be much appreciated, thanks.

Answer 1

Your readData is wrong. You read data in a local object, Data d_data(dataRows,10); which is then destroyed at the end of the function. You are not filling in the data on your current instance. You need to read directly into `p'
inp >> p[i * rows_ + j];
or use the operator() you defined on the current instance, like
inp >> (*this)(i,j); // this is preferable
Side issue: you are missing the declaration of p in the class header file, int *p;.
Side issue 2: Your int& Data::operator()(int Rows, int Cols) is confusing, try using int& Data::operator()(int i, int j), and return p[i * _cols + j]; as it makes it much easier to read.