From: kagel AT quasar DOT bloomberg DOT com
Date: Mon, 3 Feb 1997 12:15:02 -0500
Message-Id: <9702031715.AA21964@quasar.bloomberg.com >
To: an118 AT chebucto DOT ns DOT ca
Cc: djgpp AT delorie DOT com
In-Reply-To: <5d2sdh$jhj@News.Dal.Ca> (an118@chebucto.ns.ca)
Subject: Re: NEED HELP passing multi-dim arrays to functions
Reply-To: kagel AT dg1 DOT bloomberg DOT com

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   From: an118 AT chebucto DOT ns DOT ca (Graham Howard Wile)
   Newsgroups: comp.os.msdos.djgpp
   Date: 2 Feb 1997 20:11:29 GMT
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	   I have a problem with passing multi-dimensional arrays to my function. 
   Can anyone show me how to pass multi-dimensional arrays to functions?

	   The following code always works fine for a single dimensional array, 
   but not multi-dim's like the one in the example below (also, see my compiler 
   output below that):



   #include <iostream.h>

   void print_array(int *);

   void main()
	   {
	   int array1[3][3];


	   array1[0][0] = 1;
	   array1[0][1] = 2;
	   array1[0][2] = 3;

	   array1[1][0] = 4;
	   array1[1][1] = 5;
	   array1[1][2] = 6;

	   print_array(array1);
	   }


   void print_array(int * par_array1)

If the second subscript is fixed, ie always 3, you can use:

   void print_array( int *par_array1[3] )
and you should pass the magnitude of the first dimension unless it is fixed also.

Otherwise, if both dimensions are variable, the function to handle this would be:


   void print_array(int * par_array1, int rows, int cols)
                                                    ^^ # of elems in second dimension
                                          ^^ # of elems in first dimension
	   {
	   int d1, d2;

	   for (d1=0; d1 < rows; d1++)
	      for (d2=0; d2 < cols; d2++)
	         cout << "array1[" << d1 <<"][" << d2 <<"]:\t" 
			<< par_array1[(d1*(cols-1)+d2] << endl;
                 /*                   ^^^^^^^^^^^^^^^  - Here's the relevant 
							calculation. */
           }



   Here's what I get for my compiler errors:

   c:\c_progra.ms>gxx testing.cc -o testing.exe
   testing.cc: In function `int main(...)':
   testing.cc:19: passing `int (*)[3]' as argument 1 of `print array(int *)'
   testing.cc: In function `void print_array(int *)':


   This one it gives for lines 26-28, 30-32...

   testing.cc:26: invalid types `int[int]' for array subscript


-- 
Art S. Kagel, kagel AT quasar DOT bloomberg DOT com

A proverb is no proverb to you 'till life has illustrated it.  -- John Keats