Classes:memberfunction doesnt access right pointer

[slashbored]

Hi,
my task is to print the dynamic array "tensor", which is can be accessed through a private pointer "***tensor". The function "print()" is a member-function of the class Tensor3S.
At first the program creates the dynamic array and fills it with floating-point numbers provided by the file "filename.txt". This is done by the non-standard constructor, Tensor3S(const unsigned int n, const char* filename), of the class Tensor3S.
Here is how I did it:

#include<fstream>
#include<iostream>
#include<iomanip>
using namespace std;

class Tensor3S {
private:
  unsigned int n;            // Length Tensor
  double*** tensor;          // Pointer on tensor
  Tensor3S();                

public:
  Tensor3S(
      const unsigned int size, 
      const char* filename);    
  ~Tensor3S();  


  void print();	  
};

(This is the 5.cpp)

#include<iostream>
#include<iomanip>
#include "5.hpp"

using namespace std;

Tensor3S::Tensor3S(const unsigned int size, const char* filename){

	double ***tensor = new double**[size];
                 for(int i=0;i<size;i++){
		 tensor[i] = new double*[size];
 			for(int j=0;j<size;j++){
 			tensor[i][j] = new double[size];
 			}
 		}

	for(int i=0;i<size;i++){
	 for(int j=0;j<size;j++){
	  for(int k=0;k<size;k++){
	cin >> tensor[i][j][k];
// In this scope I can print the data via "cout << tensor[i][j][k];"
	  }
  }
	}
// Every adress can be printed
// These are for testing reasons and to remind myself how dynamic arrays and 
// the * work
cout 	<< "tensor=" << tensor << endl;
cout	<< "*tensor=" << *tensor << endl;
cout 	<< "**tensor=" << **tensor << endl;
cout 	<< "&(***tensor)=" << &(***tensor) << endl;


// And the print function

void Tensor3S::print(){

cout	<< "tensor=" << tensor << endl; // this gives another adress than
                                        // the tensor in the constructor
cout	<< "*tensor=" << *tensor << endl; // this too is another adress
//cout	<< **tensor << endl;              // core dumped



for(int i=0;i<3;i++){
	for(int j=0;j<3;j++){
		for(int k=0;k<3;k++){

cout	<< setw(5) << i
	<< setw(5) << j
	<< setw(5) << k
//	<< setw(12) << tensor[i][j][k] // core dumped
	<< endl;
				}
			}
		}
	}

The main.cpp looks like this:

#include"5.hpp"
#include<iostream>
#include<fstream>
#include<istream>
#include<cmath>
using namespace std;

int main(){

	int number_lines = 0;
	string line;
	ifstream myfile("filename.txt");

	while(getline(myfile, line)){
	++number_lines;
	}

cout	<< "#lines = " << number_lines << endl;  // #lines = 27


	int n = exp(log(number_lines)/3); // calculates the 3rd derivates for
                                          // which is the max length 
cout	<< "n=" << n << endl;             // n=3  

	char filename[8]; 



Tensor3S test(n, filename);

	test.print();


	return 0;
	}

Question now is:
How do I get the three dimensional array via pointer into the print-function?

Further notice:
5.hpp may not be edited.
Yes, this is an assignment.
I don't want the solution and only copy it, I want your advice what went wrong and get it done by myself.

Greeting,
/bored

[coder777]

The problem is on line 9 in 5.cpp: tensor is a local variable that hides the member variable tensor in 5.hpp. So in print() you use the member variable tensor which is not initialized

[slashbored]

At first thanks for your help!
Just for me to understand better:
The code

double ***tensor = new double**[size];
// ...  

initialized a new local variable which was deleted after the program left the constructor.
As I wanted to write the adresses into the existing private variable or in this case pointer,
I should've used the variable I already declared (double*** tensor).
This is correct, right?

This means the correct code looks like:

tensor = new double**[size];
                 for(int i=0;i<size;i++){
		 tensor[i] = new double*[size];
 			for(int j=0;j<size;j++){
 			tensor[i][j] = new double[size];
 			}
 		}

Now everything works just fine. Thanks again!

[coder777]

This is correct, right?

Exactly