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

[Douglas Bates]

On Tue, Nov 1, 2011 at 3:32 PM, Michael Hannon <jm_hannon at yahoo.com> wrote:
>
>
> 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.

Or go into Rcpp/inst/include/Rcpp/generated/vector__create.h and
extend the limit of 20.

In most cases if your list is getting very long you might want to
consider another data structure or using something other than the
::create method for the List class to create your list.  The ::create
method is a convenience construction to be able to quickly generate a
List or other type of Vector (in the Rcpp sense) object, including
assigning names.  It would be unusual to hard-code a call to
List::create with more than 20 elements.

> 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
>>
> _______________________________________________
> Rcpp-devel mailing list
> Rcpp-devel at lists.r-forge.r-project.org
> https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel