[Rcpp-devel] Rcpp equivalent of sample()?

[Chris DuBois]

Thanks Dirk.  Passing the addition function in the includes argument worked
great.

Also, one of the links from your suggested Google search led me to this
(working) example for std::accumulate:

src <- 'NumericVector xx(x);
return wrap( std::accumulate( xx.begin(), xx.end(), 0.0));'
fx <- cxxfunction(signature( x = "numeric" ),body=src,plugin = "Rcpp")
fx(1:10)  # 55

I had been copying the quickref and using:  std::accumulate( xx.begin(),
xx.end(),std::plus<double>(),0.0)

I think this might be a typo where the last two arguments are transposed
(which I shouldn't have noticed after browsing the function's c++
reference<http://www.cppreference.com/wiki/algorithm/accumulate>),
as the following works just fine:  std::accumulate( xx.begin(),
xx.end(),0.0,std::plus<double>())

Chris

On Sat, May 14, 2011 at 5:29 PM, Dirk Eddelbuettel <edd at debian.org> wrote:

>
> On 14 May 2011 at 17:13, Chris DuBois wrote:
> | Thanks Dirk.  Quick newbie followup question: Can we put functions within
> the
> | inline C++ code?  The following doesn't compile, for example:
> | src <- '
> | int addition (int a, int b)
> | {
> |   int r;
> |   r=a+b;
> |   return (r);
> | }
> | NumericVector xx(x);
> | return(xx);
> | '
> | testfun = cxxfunction(signature(x="numeric"),body=src,plugin="Rcpp")
>
> Use the 'verbose=TRUE' to cxxfunction() and it will become clear
> why -- a function is written around the 'body=...' argument,
> hence no chance that that part may contain another C++ function.
>
> The remedy is simple: use the "include=..." argument as in
>
>   inc <- '
>    int addition (int a, int b) {
>      int r = a + b;
>     return (r);
>   }
>   '
>
>   src = '
>    NumericVector xx(x);
>   return(xx);
>   '
>
>    testfun = cxxfunction(signature(x="numeric"), body=src, include=inc,
> plugin="Rcpp")
>
>
> That trick is used a couple of time in the documentation and examples.
>
>
> | On a related note, would you mind showing a quick working example using
> | std::accumulate?  The one below from the quick reference doesn't compile
> for
> | me.
>
>
> Try Google for something like that, eg a query that is restricted to my
> site as in
>
>    site:dirk.eddelbuettel.com  "std::accumulate"
>
> show five immediate hits.  You can similarly constrict the search
> to the rcpp-devel list.
>
> Can you send a small example for inline that shows how/where it quickref
> example fails for you?
>
> Dirk
>
> --
> Gauss once played himself in a zero-sum game and won $50.
>                      -- #11 at http://www.gaussfacts.com
>
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