Passing Arrays into Functions

So far, we've seen two ways of passing information into functions : call by value and call by reference. When we pass arrays into functions, it is always call by reference (at least for the scope of this course). As we shall see, there is no & character, but the array is still passed by call by reference.

Consider the following :

// file : pass.C
#include <iostream.h>
const int size=5;

void print(int n[size])
{
  int i;

  for (i=0 ; i<size ; i++)
    cout << n[i] << " ";
  cout << endl;
}

void change(int n[size])
{
  int i;

  for (i=0 ; i<size ; i++)
    n[i] =  10 + i;
}

int main()
{
  int A[size];
  int i;

  for (i=0 ;  i<size ; i++)
    A[i] = i*i;

  print(A);
  change(A);
  print(A);

  return 0;
}

Here's an example of how to pass a two dimensional array into a function :

// file : pass_2d.C
#include <iostream.h>

const int ROWS=3; const int COLS=2;

void change(int a[ROWS][COLS])
{
  int r,c;

  for (r=0 ; r<ROWS ; r++)
    for (c=0 ; c<COLS ; c++)
      if (c*r % 2 == 0)
        a[r][c]=1;
}

void print(int a[][COLS])
{
  int r,c;

  for (r=0 ; r<ROWS ; r++)
    {
      for (c=0 ; c<COLS ; c++)
	cout << a[r][c] << " ";
      cout << endl;
    }
}

int main()
{
  int X[ROWS][COLS];
  int r,c;

  for (r=0 ; r<ROWS ; r++)
    for (c=0 ; c<COLS ; c++)
      X[r][c]=0;

  change(X);
  print(X);

  return 0;
}