Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!lll-tis!ames!hc!hi!kurt
From: kurt@hi.unm.edu (Kurt Zeilenga)
Newsgroups: comp.lang.c
Subject: Re: Allocating a two-dimensional array
Message-ID: <22941@hi.unm.edu>
Date: 17 Jan 88 21:12:31 GMT
References: <1050@ogg.cgrg.ohio-state.edu>
Reply-To: kurt@hi.unm.edu (Kurt Zeilenga)
Organization: U. of New Mexico, Albuquerque
Lines: 24

Spencer@ogg.cgrg.ohio-state.edu (PROCEED) writes:
>Maybe this can't be done.  Maybe I'm not thinking about it the right way.
>But I can't figure out how to dynamically allocate a two-dimensional 
>array of floats.  (I have to have an N by N matrix of floats, but don't
>know N beforehand.)  Can anyone help me on this one?  Thanks.

You can not allocate multi-dimensional arrays dynamically.  However,
you can do is something like:

#define malloc_matrix(p,n,m,t) ((p) = ((t) *) malloc((n)*(m)*sizeof(t)))
#define matrix(p,n,m,x,y)      ((p)[(n)*(x)+(y)])

where
	t = element type
	p = pointer to type
	n,m = dimensions
	x,y = indexes

malloc_matrix() allocates the space and matrix() is used to pick the
element.

There are many similiar macros that will do the same thing, these ones
may be an overkill.
-- 
	Kurt (zeilenga@hc.dspo.gov)