Le 07/01/12 17:04, Douglas Bates a écrit :
2012/1/7 Romain François<rom...@r-enthusiasts.com>:
Le 06/01/12 20:46, Douglas Bates a écrit :
On Fri, Jan 6, 2012 at 1:12 PM, Dirk Eddelbuettel<e...@debian.org> wrote:
On 6 January 2012 at 12:59, Douglas Bates wrote:
| On Fri, Jan 6, 2012 at 12:39 PM, John Chambers<j...@stat.stanford.edu>
wrote:
|> The "Rf_" part of the API in particular is ugly and somewhat of an
add-on
|> forced in a few examples by the use of some common names in the macro
files.
|
| But, as it stands, that is a requirement when using Rcpp.
Where? I can think of one propagated use, which is at the bottom of the
try/catch structure where we use ::Rf_error. But the commonly used
macros
hide it, and we could/should obviously wrap this.
Otherwise, and especially since the 'Rcpp sugar' initiative took off, I
don't
really touch any ::Rf_* myself anymore. Inside the Rcpp code base, sure.
But
not really in user-facing stuff and Rcpp applications.
I didn't make myself clear. What I meant was that it is not possible
to use asInteger in Rcpp and count on the name being remapped to
Rf_asInteger.
| I think of the Rf_ part as more due to the fact that C doesn't have a
| concept of namespaces so anything in the R API is at the top level
| namespace leading to some conflicts.
Agreed. But speaking stylistically, for the same reason that we prefer
C++
versions of C header files (eg cstdint over stdint.h, cstdio over
stdio.h,
...) I am with John on the preference for C++ idioms when given a choice.
I suppose I could have just checked whether Rcpp::as<int> calls
Rf_asInteger. If so, everything is cool. Unfortunately, I haven't
been able to find that specialization.
as lives in the inst/include/Rcpp/as.h file, and we have to follow template
wizardry:
it starts from :
template<typename T> T as( SEXP m_sexp) {
return internal::as<T>( m_sexp, typename
traits::r_type_traits<T>::r_category() ) ;
}
with T=int, so we end up calling this one:
template<typename T> T as( SEXP x, ::Rcpp::traits::r_type_primitive_tag ) {
if( ::Rf_length(x) != 1 ) throw ::Rcpp::not_compatible(
"expecting a single value" ) ;
const int RTYPE = ::Rcpp::traits::r_sexptype_traits<T>::rtype ;
SEXP y = PROTECT( r_cast<RTYPE>(x) );
typedef typename ::Rcpp::traits::storage_type<RTYPE>::type
STORAGE;
T res = caster<STORAGE,T>( *r_vector_start<RTYPE,STORAGE>( y ) )
;
UNPROTECT(1) ;
return res ;
}
which does the magic. There is no calls to asInteger.
Which, to me, is the disadvantage. The asInteger function is brief,
understandable, flexible and well-tested. This may look transparent
to you but not to many others.
We could add another level of indirection and call asInteger, etc ... I
don't mind either way.
Romain
--
Romain Francois
Professional R Enthusiast
http://romainfrancois.blog.free.fr
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