Hi, Jingyu,
I post a small example below. I think this is what you want.
Best,
KK
#include <Rcpp.h>
using namespace Rcpp;
//[[Rcpp::export]]
void test(Nullable<Function> f = R_NilValue) {
if (f.isNotNull()) {
Rcpp::Rcout << "Not NULL fun" << std::endl;
Function f2(f);
f2();
} else {
Rcout << "NULL fun" << std::endl;
}
}
/* R code
> Rcpp::sourceCpp("test.cpp")
> f_test <- function() {
+ print("test fun")
+ }
> test(f_test)
Not NULL fun
[1] "test fun"
> test()
NULL fun
*/
On Fri, Nov 11, 2016 at 7:18 AM, Dirk Eddelbuettel <e...@debian.org> wrote:
>
> On 11 November 2016 at 05:53, Jingyu He wrote:
> | I've deleted the post on StackOverflow. Sorry for the ambiguity, the
> problem is
> | not arg, but the Function f.
> |
> |
> | #include <Rcpp.h>
> | using namespace Rcpp;
> | // [[Rcpp::export]]
> | RObject cppfunction(Function rfunction = NULL) {
> | if( rfunction == NULL){
> | cout << 1 + 1 << endl; // if we don't pass rfunction to
> cppfunction, run
> | something not related to rfunction()
> | }else{
> | rfunction() // if we pass rfunction to cppfunction, run it
> | }
> | }
> |
> | rfunction is an argument of cppfunction. Sometimes I need to pass
> rfunction to
> | cppfunction sometimes not. So I need to set a default rfunction
> (something like
> | NULL indicating not passing it).
> |
> | But
> | RObject cppfunction(Function rfunction = NULL)
> | doesn't work. How can I make it?
>
> Well that is a different question :) But it has a nice answer: use
>
> Rcpp::Nullable<Rcpp::Function> rfunction
>
> and test via
>
> if (rfunction.isNull())
>
> (Untested, but should work)
>
> Dirk
>
> --
> http://dirk.eddelbuettel.com | @eddelbuettel | e...@debian.org
> _______________________________________________
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>
--
Qiang Kou
q...@umail.iu.edu
School of Informatics and Computing, Indiana University
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