Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!mit-eddie!bloom-beacon!eru!luth!sunic!mcsun!unido!mikros!mwtech!martin
From: martin@mwtech.UUCP (Martin Weitzel)
Newsgroups: comp.lang.c
Subject: Re: Passing 2-D Arrays of unknown size ?
Message-ID: <566@mwtech.UUCP>
Date: 20 Dec 89 20:28:22 GMT
References: <3180@uceng.UC.EDU>
Reply-To: martin@mwtech.UUCP (Martin Weitzel)
Organization: MIKROS Systemware, Darmstadt/W-Germany
Lines: 34

In article <3180@uceng.UC.EDU> mfinegan@uceng.UC.EDU (michael k finegan) writes:
[some lines deleted]
-    Is there a method for passing/using multi-D arrays in subroutines,
[most of examples deleted]
-solution_func3(array,rows,cols)
-char *array;
-int rows, cols;
-{
-    int i,j;
-
-   /* But now I can't use array[][] notation,
-    * and must calculate the indices myself !
-    */
-    for(i ...)
-        for(j ...)
-            some_operation(array[i*cols + j]);
				  ^^^^^^^^^
Exactly this is, what a compiler would have to - and can not do
at compile time, because cols is only know at runtime. You
cannot have the array[][] notatation, but you could write a
preprocessor makro:
#define ARR(x,y) (array[(x)*cols+(y)]) to make the following
a (little) more readable:
-
-   /* with typically: array[(long calculated value)*stride*cols +
-    *					stride*(another calculated value)]
-    */
ARR((long calculated value)*stride, stride*(another calculated value)).

Of course, you could consider a switch to C++, where you could overload
the []-Operator ...

-- 
Martin Weitzel, email: martin@mwtech.UUCP, voice: 49-(0)6151-6 56 83