[Rcpp-devel] Multiplication of ComplexVector?

[Romain Francois]

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

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Romain Francois
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