[Rcpp-devel] function modifying it self its argument

[Pierre GLOAGUEN]

Ok, i'll do this.
Thanks and have a nice day,

Pierre

Le 26/02/2015 16:51, Dirk Eddelbuettel a écrit :
> On 26 February 2015 at 16:37, Pierre GLOAGUEN wrote:
> | Thanks, it works!
> | I'm not familiar with C++, is it necessary to always use such a function in C++
> | or is it because of R/C++ interface?
>
> Please use a Google search (or equivalent) for Rcpp::clone.  This has been
> discussed extensively on numerous occassions.
>
> Dirk
>
> | Thanks again for your help,
> |
> | Pierre
> |
> | Le 26/02/2015 16:30, Jeffrey Pollock a écrit :
> |
> |     Perhaps use the clone() function?
> |
> |     library(Rcpp)
> |
> |     cppFunction("
> |     NumericVector par_CMAtR(NumericVector vec_CMA) {
> |         NumericVector out = clone(vec_CMA);
> |         out[5] = exp(out[5]);
> |         return out;
> |     }
> |     ")
> |
> |     vec_C<- rep(1, 6)
> |     par_CMAtR(vec_C)
> |     print(vec_C)
> |
> |     On Thu, Feb 26, 2015 at 3:16 PM, Pierre GLOAGUEN<
> |     Pierre.Gloaguen at ifremer.fr>  wrote:
> |
> |
> |         Hello everybody,
> |
> |         I have a very simple example
> |         I have a vector vec_CMA which length is a multiple of 6.
> |         I want to get the exact same vector, except the last element which is
> |         the exponential of the last element of vec_CMA
> |         The code is the following
> |
> |         //myfun.cpp
> |         #include<Rcpp.h>
> |         using namespace Rcpp;
> |
> |         // [[Rcpp::export]]
> |         NumericVector par_CMAtR(NumericVector vec_CMA){
> |           int K = (vec_CMA.size())/6;
> |           NumericVector out(6*K);
> |           out = vec_CMA;
> |           out[6*K-1] = exp(vec_CMA[6*K-1]);
> |           return out;
> |         }
> |
> |         I apply the function with the R code
> |         sourceCpp("myfun.cpp")
> |         vec_C<- rep(1,6)
> |         par_CMAtR(vec_C)
> |         [1] 1 1 1 1 1 2.718282
> |
> |         8
> |
> |         works fine. Except the vec_C is modified too!
> |         vec_C
> |         [1] 1 1 1 1 1 2.718282
> |
> |         It's the first time I have this kind of problem. What is wrong in my
> |         code?
> |         Thanks for your help,
> |
> |         Pierre Gloaguen
> |
> |
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