Re: A Matrix collection class
Re: A Matrix collection class
- Subject: Re: A Matrix collection class
- From: Ondra Cada <email@hidden>
- Date: Wed, 8 May 2002 15:52:03 +0200
On Wednesday, May 8, 2002, at 02:46 , email@hidden wrote:
My main problem with multidimensional arrays is figuring out how to
convert a straight void* to them - I can never persuade C to convert to
int[x][y][]...
On the plain C level, you want to convert to int* instead of int[], so
something like ((int*)[x][y]) should work. Remember, in plain C, a[x] and
*(a+X) are equivalent expressions. Also, for some not quite obvious reason,
this works for me only if typedef is used (anybody knows why cast '((*int)
[5][3])' does not work? It should, IMHO!):
27 /tmp> cat q.c
#include <stdio.h>
int main() {
int i,j,k,a[10][5][3];
void *ptr=(void*)a;
typedef int (*foo)[5][3];
for (i=0;i<10;i++) for (j=0;j<5;j++) for (k=0;k<3;k++) a[i][j][k]=i^j^k;
for (i=0;i<10;i++) for (j=0;j<5;j++) for (k=0;k<3;k++)
if (a[i][j][k]!=((foo)ptr)[i][j][k]) {
printf("Oops at %d,%d,%d\n",i,j,k);
return 1;
}
printf("OK\n");
return 0;
}
28 /tmp> cc -Wall q.c && ./a.out
OK
29 /tmp>
And while I know I can use my own index calculation, or an NSDictionary,
I was hoping (as I said) for something less ugly. An object that does
that for me, for example.
I personally know of none available, but my estimate for writing and
debugging one is half an hour at most for relatively inexperienced
programmer, so I would not see it as a big problem.
---
Ondra Cada
OCSoftware: email@hidden
http://www.ocs.cz
2K Development: email@hidden
http://www.2kdevelopment.cz
private email@hidden
http://www.ocs.cz/oc
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