Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!rutgers!sri-spam!mordor!lll-tis!ames!amdcad!sun!aeras!dgcad!catsim!altnet!altos86!nate
From: nate@altos86.UUCP (Nathaniel Ingersoll)
Newsgroups: comp.lang.c
Subject: Re: Two dimensional arrays in C
Message-ID: <344@altos86.UUCP>
Date: Wed, 24-Jun-87 12:13:43 EDT
Article-I.D.: altos86.344
Posted: Wed Jun 24 12:13:43 1987
Date-Received: Sat, 27-Jun-87 13:59:13 EDT
References: <733@cod.UUCP>
Reply-To: nate@altos86.UUCP (Nathaniel Ingersoll)
Organization: Altos Computer Systems, San Jose, CA
Lines: 56
Keywords: ?

In article <733@cod.UUCP> murphys@cod.UUCP (Steven P. Murphy) writes:
...declarations...
>static double data1[ROWS][COLUMNS];
>static double data2[ROWS][COLUMNS];

make that
	static double data1[ROWS1][COLUMNS1];
	static double data2[ROWS2][COLUMNS2];
>
>int n, m;
>
>n1 = 300;
>m1 = 15;
>  .
>matrix_stuff(n1, m1, data1, ROWS1, COLUMNS1);
>  .
>matrix_stuff(n2, m2, data2, ROWS2, COLUMNS2);
>}
>
>matrix_stuff(a, b, array, x, y);
>int a, b, x, y;
>double array[x][y];
>{
>int i, j;
>   .
>for(i = 0;i <= a;i++)                  /* step through the rows */
>   for(j = 0;j <= b;j++)               /* step through the columns */

The problem here is with the
	double array[x][y];
declaration.  You need to declare all the sizes of an arrays
dimensions except the first; and this declaration must be _constant_.
To do what you want you would probably have to do something like

/*
*	note that the x array bound is unneeded
*
*	various purists will probably be offended by the
*	following declaration for "array"
*/
matrix_stuff(a, b, array, x, y)
	int a, b, x, y;
	double *array;
{
#define		place(u, v)	((u)*y + (v))
	int i, j;

	/* following with your example, though you'd probably want
	to eliminate the a and b parameters  and use x and y instead */
	for (i = 0;i < a;i++)
		for (j = 0;j < b;j++)
/*
			...use array[place(i, j)] in here....
for example, this would  mutiply all elements of array by 2:
			array[place(i, j)] *= 2;
*/
}