On 01/14/2010 02:27 PM, Laurent Gautier wrote:
On 1/14/10 1:16 PM, Romain Francois wrote:
On 01/14/2010 12:42 PM, Laurent Gautier wrote:
Hi,
In Rcpp, we now have a "Function" class to encapsulate functions
(they cover all three kinds, but this may change).
Just a note on that: there is probably no hurry to do so.
rpy2 is also having CLOSXP, BUILTINSXP, and SPECIALSXP represented as
one function-like class and seems to be behave reasonably while a lot of
other things seem more urgent to sort out.
To call the function, what we do is generate a call with the function
as the first node and then evaluate the call.
SEXP stats = PROTECT( R_FindNamespace( mkString( "stats") ) ); SEXP
rnorm = PROTECT( findVarInFrame( stats, install( "rnorm") ) ) ; SEXP
call = PROTECT( LCONS( rnorm, CONS( ScalarInteger(10),
CONS(ScalarReal(0), R_NilValue ) ) ) ); SEXP res = PROTECT( eval(
call , R_GlobalEnv ) ); UNPROTECT(4) ; return res ;
It works, but I was wondering if there was another way. I've seen
applyClosure, but I'm not sure I should attempt to use it or if using
a call like above is good enough.
Using R_tryEval() will let you evaluate an expression in a given
environment, as well as capture an eventual error occurring during its
evaluation (and translate it as an exception).
Sure. I did not want to over-complicate the question.
I'm currently reviewing tryEval and its underlying R_TopLevelExec which
does not give me enough : when the error occurs, it'd be useful that the
function returns the condition object instead of NULL.
I possibly went the same path, and ended with R_tryEval. When looking at
it, I could not figure out any way to get what I wanted outside using
"geterrmessage" in base.
The error string is in the variable errbuf (in src/main/error.c), with
no obvious route to access it (and if truly no route, this might be
something missing from the R C-API).
It seems to be the regular way around this gap. Martin Morgan gave the
same advice (using geterrmessage) here last week. it only gives you the
error message though
I've been staring at R_ToplevelExec, begincontext and addCondHands. Some
day, I'll understand how to connect the dots. Not today though.
Romain
Romain
PS: using Rcpp's C++ classes you would express the code above as :
Environment stats("package:stats") ; Function rnorm = stats.get(
"rnorm" ) return rnorm( 10, 0.0 ) ;
Feel free to snoop in rpy2's rpy/rinterface/rinterface.c and look for
"do_try_eval". The behavior looks very similar, the above snippet in
rpy2 would write like:p/
I meant "do_eval_expr".
thanks.
from rpy2.robjects.packages import importr
stats = importr('stats')
stats.rnorm(10, 0.0)
nice
--
Romain Francois
Professional R Enthusiast
+33(0) 6 28 91 30 30
http://romainfrancois.blog.free.fr
|- http://tr.im/KfKn : Rcpp 0.7.2
|- http://tr.im/JOlc : External pointers with Rcpp
`- http://tr.im/JFqa : R Journal, Volume 1/2, December 2009
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
