From btyner at stat.purdue.edu  Mon Nov 20 14:41:39 2006
From: btyner at stat.purdue.edu (Benjamin Tyner)
Date: Mon, 20 Nov 2006 08:41:39 -0500
Subject: [Rd] array indexes in C
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Message-ID: <4561B093.4080800@stat.purdue.edu>

Tamas,

I am using GCC with no problems. You can find more examples at
http://gcc.gnu.org/onlinedocs/gcc-3.3.1/gcc/Variable-Length.html

Ben
> Hi Ben,
>
> Thanks for your answer.  I looked at the status of VLA on the GCC
> homepage and it appears to be "broken". [1] Do you think that the code
> below still works?  Or are you using a different compliler?
>
> Thanks,
>
> Tamas
>
> [1] http://gcc.gnu.org/c99status.html
>
>
> On Sun, Nov 19, 2006 at 09:55:17AM -0500, Benjamin Tyner wrote:
>   
>> Tamas,
>>
>> You could write convenience functions, but I have used the C99 mechanism 
>> for variable length arrays with no problems calling from R. One thing 
>> you have to keep in mind though is that (as far as I know) the 
>> dimensions must be passed before the array reference. So for example,
>>
>> r <- .C("foo",
>>               as.integer(ni),
>>               as.integer(nj),
>>               x = double(ni * nj),
>>               ...)
>>
>> with your function defined as
>>
>> void foo(int *ni, int *nj, double x[*ni][*nj])
>> {
>> ...
>>
>> Then in C you can access elements of x via x[3][4], for example.
>>
>> Ben
>>
>> ______________________________________________
>> R-devel at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel



[Rd] array indexes in C
Benjamin Tyner