[Rcpp-devel] Rcpp-devel Digest, Vol 14, Issue 17
romain at r-enthusiasts.com
Sun Dec 5 09:26:01 CET 2010
Le 05/12/10 03:50, Christian Gunning a écrit :
> On Sat, Dec 4, 2010 at 7:35 AM,
> <rcpp-devel-request at lists.r-forge.r-project.org> wrote:
>> While I am on this, would it be valuable to have something like this:
>> typedef SubMatrix<REALSXP> NumericSubMatrix ;
>> or perhaps inside Matrix we could have:
>> typedef typename SubMatrix<RTYPE> sub ;
>> So that we would write
>> NumericMatrix::sub yy = xx( Range(0,2), Range(0,3) )
> Looks nice. I was wondering about that.
I was just enquiring about it. This is not commited yet.
> Question -
> Is there a simple example where the following differ? I looked at the
> source, and it looks to me that MatrixColumn, MatrixRow, and SubMatrix
> objects are still tied to the original Matrix object (example 1),
That definitely is the intention.
> whereas example 2 creates an entirely new object. I don't understand
> the exact consequences of this. Am I correct in assuming that A, 1
> does not make a new copy, and that B, modifications to the SubMatrix
> object propogate back to the underlying Matrix?
> 1) NumericMatrix::sub yy1 = xx( Range(0,2), Range(0,3) )
> 2) NumericMatrix: yy2 = xx( Range(0,2), Range(0,3) )
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