How to pass arbitrary 2-d array argument ?

[Tom Stockfisch]

In article <1991Jan6.044056.23028 at noose.ecn.purdue.edu> luj at delta.ecn.purdue.edu (Jun Lu) writes:
>It would be nice if I can have a "subroutine" which takes arbitrary matrices as
>arguments and performs some operations on them. The dimensions of the 2-d
>array are not known a priori.

I'm so proud of my clever programming constructs for this I just have to
post every time this topic comes up (-:
Using your code with my method for handling 2-d arrays in C,

main()
{
     double m1[4][2], m2[4][2], m[4][2];

     /* init m1, m2 ... */


     madd(m1[0], m2[0], m[0], 4, 2);
     /* ... */
}

madd( a, b, c, m, n )
	double	a[/* m*n */], b[/* m*n */], c[/* m*n */];
#		define A(i,j)	( (i) *n+ (j) )
#		define B(i,j)	( (i) *n+ (j) )
{
	int	i, j;

	for (i = 0; i < m; i++)		/* fucntionality of madd() */
		for (j = 0; j < n; j++)
	    		C(i,j) = A(i,j) + B(i,j);
}

Note the missing declarations for m,n.  This is because they appear in
the comments inside the array dimensions.
Note the macro definitions are analogues of the Fortran "dimension" statement.


>No calling Fortran from C please. 

Certainly not for this.
-- 

|| Tom Stockfisch, UCSD Chemistry	tps at chem.ucsd.edu