help converting multi-dim arrays

Donn Seeley donn at utah-cs.UUCP
Sun Apr 14 17:19:43 AEST 1985

It's not strictly necessary to have an array of pointers to provide a
multi-dimensional array that varies in size, provided the variation is
limited to one dimension.  The following example shows one way to
dynamically allocate a multi-dimensional array:

# define	MAXROWS		10000
# define	MAXCOLS		1000

f( nrows )
	int		nrows;
	register double	(*dp)[MAXROWS][MAXCOLS];
	char		*malloc();

	dp		= (double (*)[MAXROWS][MAXCOLS])
			  malloc( nrows * MAXCOLS * sizeof (double) );
	if ( dp == NULL )
		bomb( "Out of memory" );
	(*dp)[1][0]	= 1.0;
	free( (char *) dp );

I believe this is portable code, going on the basis of section 14.3 of
the C reference manual, but I'd be happy to be corrected if wrong.
(Actually, the main reason I like this example is that it provides a
rare instance of a use for one of the more bizarre C type

Donn Seeley    University of Utah CS Dept    donn at
40 46' 6"N 111 50' 34"W    (801) 581-5668    decvax!utah-cs!donn

More information about the Comp.lang.c mailing list