string comparison
It is not safe to rely on pointer comparisons until R 2.8.0. Currently it
is easy to get CHARSXPs that are not in the cache: it is not impossible in
2.8.0, but you have to know how to 'break and enter'.
In your code you are comparing a CHARSXP and a SYMSXP. You want to
use charChance = mkChar("chance") and then make it precious
(R_PreciousObject).
On Thu, 7 Aug 2008, Kjell Konis wrote:
Hi,
I have a package where I do things like this a lot:
if(strncmp(CHAR(asChar(Scategory)), "chance", 6) == 0)
category = h_category_chance;
else if(strncmp(CHAR(asChar(Scategory)), "utility", 7) == 0)
category = h_category_utility;
else if(strncmp(CHAR(asChar(Scategory)), "decision", 8) == 0)
category = h_category_decision;
else if(strncmp(CHAR(asChar(Scategory)), "instance", 8) == 0)
category = h_category_instance;
else
category = h_category_error;
I would like to replace the strncmps with pointer comparisons so I set up
some global variables in the R_init_myDLL function like this:
charChance = install("chance")
<etc.>
but I can't seem to get the comparison to work. I want to do something like
if(CHAR(asChar(Scategory)) == charChance)
category = h_category_chance;
but category always ends up being h_category_error. Any pointers would be
appreciated.
Thanks,
Kjell
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Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595