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double array

Posted on 1998-07-03
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Last Modified: 2010-08-05
Hi

I have problems passing a double array to a function.
I wrote two examples.
One involves a simple array. It works.
The second involves a double array.Id doesn.t.


First example

#include<stdio.h>
#include<iostream.h>

void printArray(int*);

int theArray[8];
int anotherArray[8];

void printArray(int* givenArray)
{
      for(int i = 0; i < 8; i++)
      {
            cout << givenArray[i] << endl;
      }
}


int main()
{

      for(int i = 0; i < 8; i++)
      {
            theArray[i] = i;
            anotherArray[i] = 10 + i;
      }

      printArray(theArray);
      cout << endl;
      printArray(anotherArray);

      return 0;
}


Second example:
#include<iostream.h>


void printArray(int**);



int theArray[8][8];
int anotherArray[8][8];

void printArray(int** givenArray)
{
      for(int i = 0; i < 8; i++)

            for(int j = 0; j < 8; j++)

                  cout << givenArray[j][i] << endl;

}

int main()
{
     for(int i = 0; i < 8; i++)
     {
      for(int j = 0; j < 8; j++)

             {
                  theArray[j][i] = i;
                  anotherArray[j][i] = j;
            }
     }



     printArray(theArray);
     cout << endl;
     printArray(anotherArray);

     return 0;
}


The error message that I get is"can not convert int[8]*
to **".

I understand that in the case of a single array,
theArray is equivalent to *theArray[0];

A pointer to the first member of the array.
I think that in case of a double array, we deal with a pointer to the first element of the array wich is an array itself that means is a pointer to the first element of the array.
So in case of a double array we deal with a pointer to a pointer.
When I passed the simple array to the function it was ok, because the function was defined as receiving a pointer to an integer and theArray was a pointer to an integer.

The second time, the function is defined as receiving a pointer to a pointer to an integer. theArray is a pointer to a pointer to a integer, still the program complains.

Thank you.
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Question by:simi
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Accepted Solution

by:
alex_r earned 200 total points
ID: 1167134
When you are dealing with double array[x][y], it's like you are dealing with array[x*y]
(It's wha's the complier do: "converts" array[2][3] to array[2 * y + 3])
So you must "to give" to compiler the "y"

So. you must your define function like this:
void printArray(int givenArray[][8])
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