[Rcpp-devel] Limit of 20 on length of Rcpp::List::create?

[Michael Hannon]

Greetings.  It appears that there is a limit of 20 items in a list created by;

    Rcpp::List:create

I.e., the appended code works as expected if I omit all references to "x21",
but fails with an error (shown below, after the code example) when I include
"x21".  (The successful output shown below is, obviously, for the case in
which "x21" was NOT included.)

A workaround appears to be just to pack the items into sublists and return the
sublists.  I just want to be sure I've understood correctly.

Thanks,

-- Mike


#+BABEL: :session *R* :cache yes :results output verbatim :exports both :tangle yes

* Return a long list

#+begin_src R
    library(Rcpp)
    library(inline)

    includes = '
    '

    ccode = '
      int x1  (1);
      int x2  (2);
      int x3  (3);
      int x4  (4);
      int x5  (5);
      int x6  (6);
      int x7  (7);
      int x8  (8);
      int x9  (9);
      int x10 (10);
      int x11 (11);
      int x12 (12);
      int x13 (13);
      int x14 (14);
      int x15 (15);
      int x16 (16);
      int x17 (17);
      int x18 (18);
      int x19 (19);
      int x20 (20);
      int x21 (21);

      return (Rcpp::List::create(
                  Rcpp::Named("x1")  = x1,
                  Rcpp::Named("x2")  = x2,
                  Rcpp::Named("x3")  = x3,
                  Rcpp::Named("x4")  = x4,
                  Rcpp::Named("x5")  = x5,
                  Rcpp::Named("x6")  = x6,
                  Rcpp::Named("x7")  = x7,
                  Rcpp::Named("x8")  = x8,
                  Rcpp::Named("x9")  = x9,
                  Rcpp::Named("x10") = x10,
                  Rcpp::Named("x11") = x11,
                  Rcpp::Named("x12") = x12,
                  Rcpp::Named("x13") = x13,
                  Rcpp::Named("x14") = x14,
                  Rcpp::Named("x15") = x15,
                  Rcpp::Named("x16") = x16,
                  Rcpp::Named("x17") = x17,
                  Rcpp::Named("x18") = x18,
                  Rcpp::Named("x19") = x19,
                  Rcpp::Named("x20") = x20,
                  Rcpp::Named("x21") = x21
                  )
      );
    '
    fn = cxxfunction(
      sig      = signature(),
      body     = ccode,
      includes = includes,
      plugin   = "Rcpp")

  fn()

#+end_src

#+results[0bbf13bdc92f7b08c3d0922279abf8d31332c7e0]:
#+begin_example
 $x1
[1] 1

$x2
[1] 2

$x3
[1] 3

$x4
[1] 4

$x5
[1] 5

$x6
[1] 6

$x7
[1] 7

$x8
[1] 8

$x9
[1] 9

$x10
[1] 10

$x11
[1] 11

$x12
[1] 12

$x13
[1] 13

$x14
[1] 14

$x15
[1] 15

$x16
[1] 16

$x17
[1] 17

$x18
[1] 18

$x19
[1] 19

$x20
[1] 20
#+end_example

-----

Error in compileCode(f, code, language = language, verbose = verbose) : 
  Compilation ERROR, function(s)/method(s) not created! file1a507fc6.cpp: In
function ‘SEXPREC* file1a507fc6()’:
file1a507fc6.cpp:76:17: error: no matching function for call to
‘Rcpp::Vector<19>::create(Rcpp::traits::named_object<int>,
Rcpp::traits::named_object<int>, Rcpp::traits::named_object<int>,
Rcpp::traits::named_object<int>, Rcpp::traits::named_object<int>,
Rcpp::traits::named_object<int>, Rcpp::traits::named_object<int>,
Rcpp::traits::named_object<int>, Rcpp::traits::named_object<int>,
Rcpp::traits::named_object<int>, Rcpp::traits::named_object<int>,
Rcpp::traits::named_object<int>, Rcpp::traits::named_object<int>,
Rcpp::traits::named_object<int>, Rcpp::traits::named_object<int>,
Rcpp::traits::named_object<int>, Rcpp::traits::named_object<int>,
Rcpp::traits::named_object<int>, Rcpp::traits::named_object<int>,
Rcpp::traits::named_object<int>, Rcpp::traits::named_object<int>)’
file1a507fc6.cpp:76:17: note: candidates are:
/usr/lib64/R/library/Rcpp/include/Rcpp/ve
In addition: Warning message:
running command '/usr/lib64/R/bin/R CMD SHLIB file1a507fc6.cpp 2>
file1a507fc6.cpp.err.txt' had status 1 


------

> sessionInfo()
R version 2.13.1 (2011-07-08)
Platform: x86_64-redhat-linux-gnu (64-bit)

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C               LC_TIME=en_US.UTF-8       
 [4] LC_COLLATE=en_US.UTF-8     LC_MONETARY=C
LC_MESSAGES=en_US.UTF-8   
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C                  LC_ADDRESS=C              
[10] LC_TELEPHONE=C             LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       

attached base packages:
[1] stats     graphics  grDevices datasets  utils     methods   base     
>