[Rcpp-devel] Multiplication of ComplexVector?

[Romain Francois]

Yep, that is because of RcppExport. You only use RcppExport when you 
call the function from .Call in R.

RcppExport is an alias to extern "C" so it essentially voids the 
C++-ness of the function it is applied to.

Romain

Le 18/08/10 09:05, Christian Gunning a écrit :
> I'm using a package generated by Rcpp.package.skeleton.  No C files.
> Upon reflection, I'm not entirely sure I have the header right,
> though.
>
> ///////
> // rcpp_operators.h:
> ///////
> #ifndef _Rcwttest_RCPP_OPERATORS_H
> #define _Rcwttest_RCPP_OPERATORS_H
> #include<Rcpp.h>
> RcppExport Rcomplex operator*(const Rcomplex&, const Rcomplex&);
> RcppExport Rcomplex operator*(const Rcomplex&, const double&);
> #endif
>
> ///////
> // rcpp_operators.cpp
> ///////
> #include "rcpp_operators.h"
> Rcomplex operator*( const Rcomplex&  lhs, const double&  rhs){
>         Rcomplex y ;
>         y.r = lhs.r * rhs;
>         y.i = lhs.i * rhs ;
>         return y ;
> }
> Rcomplex operator*( const Rcomplex&  lhs, const Rcomplex&  rhs){
>         Rcomplex y ;
>         y.r = lhs.r * rhs.r - lhs.i * rhs.i ;
>         y.i = lhs.r * rhs.i + rhs.r * lhs.i ;
>         return y ;
> }
>
>
> Compiler output (from "R CMD build Rcwttest; R CMD INSTALL Rcwttest;"):
>
> g++ -I/usr/share/R/include
> -I"/usr/local/lib/R/site-library/Rcpp/include"   -fpic  -g -O2 -c
> rcpp_cwt_thierry.cpp -o rcpp_cwt_thierry.o
> In file included from rcpp_cwt_thierry.cpp:2:
> rcpp_operators.h:7: error: declaration of C function ‘Rcomplex
> operator*(const Rcomplex&, const double&)’ conflicts with
> rcpp_operators.h:6: error: previous declaration ‘Rcomplex
> operator*(const Rcomplex&, const Rcomplex&)’ here
>
>
> -xian
>
> On Tue, Aug 17, 2010 at 11:30 PM, Romain Francois
> <romain at r-enthusiasts.com>  wrote:
>> Le 18/08/10 08:19, Romain Francois a écrit :
>>>
>>> Le 18/08/10 07:44, Christian Gunning a écrit :
>>>>
>>>> Thanks to all for the helpful suggestions. I was excited to learn
>>>> about Armadillo's plans for fft/ifft -- my original interest in Rcpp
>>>> was to facilitate the R fft call from C...
>>>>
>>>> For conceptual simplicity, I'm opting for manually adding an operator*
>>>> for now.
>>>
>>> Note that they will appear in the next version of Rcpp, which is
>>> scheduled (loosely) for the end of august.
>>>
>>>> Benchmarks show a ~10% speedup over sending large vectors (2
>>>> million) to R for multiplication.
>>>>
>>>> One question that I ran into that I don't quite understand -- there
>>>> are several permutations of an Rcomplex-returning operator*, depending
>>>> upon the type of lhs and rhs (e.g Rcomplex and Rcomplex; Rcomplex and
>>>> double; etc.). I admit, the template system is over my head for now,
>>>> and this has a low priority for me, but perhaps there's a simple
>>>> explanation asides from using separate operator symbols?
>>>>
>>>> Here are 2 definitions that vary in input type:
>>>>
>>>> Rcomplex operator*( const Rcomplex&  lhs, const Rcomplex&  rhs){
>>>> Rcomplex y ;
>>>> y.r = lhs.r * rhs.r - lhs.i * rhs.i ;
>>>> y.i = lhs.r * rhs.i + rhs.r * lhs.i ;
>>>> return y ;
>>>> }
>>>>
>>>> Rcomplex operator*( const Rcomplex&  lhs, const double&  rhs){
>>>> Rcomplex y ;
>>>> y.r = lhs.r * rhs ;
>>>> y.i = lhs.i * rhs ;
>>>> return y ;
>>>> }
>>>>
>>>> yielding the following compiler error:
>>>>
>>>> rcpp_operators.h:7: error: declaration of C function ‘Rcomplex
>>>> operator*(const Rcomplex&, const double&)’ conflicts with
>>>> rcpp_operators.h:6: error: previous declaration ‘Rcomplex
>>>> operator*(const Rcomplex&, const Rcomplex&)’ here
>>>>
>>>> best,
>>>> Christian
>>>
>>> Do you include this from a .c file or a .cpp file ? C has no concept of
>>> overloading.
>>>
>>> Can you share a small reproducible example that shows the problem.
>>>
>>> Romain
>>
>> It seems to work fine for me :
>>
>> require( inline )
>> require( Rcpp )
>>
>> inc<- '
>> Rcomplex operator*( const Rcomplex&  lhs, const Rcomplex&  rhs){
>>         Rcomplex y ;
>>         y.r = lhs.r * rhs.r - lhs.i * rhs.i ;
>>         y.i = lhs.r * rhs.i + rhs.r * lhs.i ;
>>         return y ;
>> }
>> Rcomplex operator*( const Rcomplex&  lhs, const double&  rhs){
>>        Rcomplex y ;
>>        y.r = lhs.r * rhs ;
>>        y.i = lhs.i * rhs ;
>>        return y ;
>> }
>>
>> '
>> fx<- cxxfunction( signature( ), '
>> using namespace Rcpp ;
>>     Rcomplex x, y ;
>>     x.r = 2.0 ; x.i = 2.0 ;
>>     y.r = 1.0 ; y.i = 1.0 ;
>>
>>     Rcomplex z = x * y ;
>>     Rcomplex a = x * 3 ;
>>     return ComplexVector::create( x, y, z, a ) ;
>>
>> ', plugin = "Rcpp", includes = inc )
>>
>>
>>
>>> fx()
>> [1] 2+2i 1+1i 0+4i 6+6i
>>
>> so I'm staying with my guess that this is a C vs C++ issue.
>>
>> Romain

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Romain Francois
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http://romainfrancois.blog.free.fr
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