[R] Avoiding deep copies

Peter Dalgaard BSA p.dalgaard at biostat.ku.dk
Tue Oct 2 16:34:04 CEST 2001

Johann Petrak <johann at ai.univie.ac.at> writes:

> Is it correct that there is no way of avoiding deep copying
> of data structures? Or asked from a different perspective,
> is it true that there are no pointers? :)
> (not that I am a fan of pointer, they just let me
> decide when to do deep copy on my own when the
> memory manager doesnt do it for me :) )
> I was considering writing code in R that would need
> the internal representation of complex graph structures
> where several nodes in the graph point to the same
> huge array of data.
> Now, obviously one cannot just do something like
> attr(thenode,"mydatavec")<-thedatavec or
> thenode$mydatavec<-thedatavec
> since all the data in thedatavec will be copied
> with this assignment.
> Are there commonly accepted/used workarounds?

Some ideas are being bandied about on this issue, but it isn't all
that easy. We've had the .Alias mechanism for a while, but it is
a very dirty hack, and people are wanting to remove it.

You could have a look at Luke Tierney's notes on this and related
matters if you care: 


   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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