consider empty vectors in min() and max() (fixes #883)

[eddelbuettel]

No description provided.

[eddelbuettel]

Reviews / thumbs up-or-down welcome! @kevinushey @jjallaire @thirdwing @nathan-russell ...

[kevinushey]

LGTM!

[coatless]

Why not use R_NaN instead of R_NegInf?

[eddelbuettel]

Because of this:

R> v <- numeric(0); c(min(v), max(v))
[1]  Inf -Inf
Warning messages:
1: In min(v) : no non-missing arguments to min; returning Inf
2: In max(v) : no non-missing arguments to max; returning -Inf
R> 

In the integer case it does become NA from the static_cast. Have not tried complex or other vectors.

[eddelbuettel]

Running another round of reverse depends now, and only hickup is in BigVAR. It has in file src/ExperimentalBigVARFunctionsX.cpp a function (indented here)

colvec ThreshUpdateOO(const mat& ZZ, double lam,const mat& Y,double eps, List groups, \
       List fullgroups, List compgroups,List M2f_, List eigvalF_, List eigvecF_, \
       colvec& B,int n, int k1) {

with a test

    if(max(groups)==0)

and we now get

ccache g++ -std=c++11 -std=gnu++11 -I"/usr/share/R/include" -DNDEBUG  -I"/usr/local/lib/R/site-library/Rcpp/include" -I"/usr/local/lib/R/site-library/RcppArmadillo/include" -I"/usr/local/lib/R/site-library/Rc\
ppEigen/include"   -DNDEBUG -fpic  -g0 -O3 -Wall -pipe -Wno-unused  -fext-numeric-literals -march=native -c ExperimentalBigVARFunctionsX.cpp -o ExperimentalBigVARFunctionsX.o                                   
In file included from /usr/local/lib/R/site-library/Rcpp/include/Rcpp/sugar/functions/functions.h:50:0,  
                 from /usr/local/lib/R/site-library/Rcpp/include/Rcpp/sugar/sugar.h:31,                  
                 from /usr/local/lib/R/site-library/Rcpp/include/Rcpp.h:74,                              
                 from /usr/local/lib/R/site-library/RcppArmadillo/include/RcppArmadillo.h:34,            
                 from ExperimentalBigVARFunctionsX.cpp:1:                                                
/usr/local/lib/R/site-library/Rcpp/include/Rcpp/sugar/functions/max.h: In instantiation of ‘Rcpp::sugar::Max<RTYPE, NA, T>::operator Rcpp::sugar::Max<RTYPE, NA, T>::STORAGE() const [with int RTYPE = 19; bool NA = true; T = Rcpp::Vector<19>; Rcpp::sugar::Max<RTYPE, NA, T>::STORAGE = SEXPREC*]’:                   
ExperimentalBigVARFunctionsX.cpp:590:20:   required from here                                            
/usr/local/lib/R/site-library/Rcpp/include/Rcpp/sugar/functions/max.h:36:32: error: invalid static_cast from type ‘double’ to type ‘Rcpp::sugar::Max<19, true, Rcpp::Vector<19> >::STORAGE {aka SEXPREC*}’       
             if (n == 0) return(static_cast<STORAGE>(R_NegInf));                                         
                               ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                          
/usr/lib/R/etc/Makeconf:168: recipe for target 'ExperimentalBigVARFunctionsX.o' failed                   
make: *** [ExperimentalBigVARFunctionsX.o] Error 1                                                       
ERROR: compilation failed for package ‘BigVAR’

but I am a little confused how that would have worked before max() over a Rcpp::List comparing to a scalar? Did that ever make sense?

Is this a regression we need to fix?

[kevinushey]

Looks like max() doesn't actually do what one might expect it to do when applied to a List:

#include <Rcpp.h>
using namespace Rcpp;

// [[Rcpp::export]]
SEXP max(List data) {
   return Rcpp::max(data);
}

/*** R
max(list(1, 2, 3, 4, 5))
*/

> Rcpp::sourceCpp('~/scratch/Untitled.cpp')
> max(list(1, 2, 3, 4, 5))
[1] 1

IMHO it's fine that this is a compilation error and perhaps provide a patch (or request a change) from BigVAR.

[kevinushey]

The R level APIs also don't understand lists:

> base::max(list(1, 2, 3, 4, 5))
Error in base::max(list(1, 2, 3, 4, 5)) : 
  invalid 'type' (list) of argument

so IMHO further evidence that not supporting Lists is fine.

[eddelbuettel]

Agreed. Did the same / similar test with max() / min() around Rcpp::List for both 0.12.17 and 0.12.18 -- results were incorrect for 0.12.17 as you show, and 0.12.18 fails to compile. With an added as<>() it compiles and still returns the wrong result :)

So I concur: It was sloppy code by us before allowing this compile, but this particular snippet may actually be an issue in BigVAR. I also contacted its maintainer, @wbnicholson.

[wbnicholson]

Thanks for letting me know about this issue. I will remove the max call from my package and will re-upload a new version to cran.

[eddelbuettel]

Awesome (as also discussed via email).

Turns out that this was the only 'regression' so I will wrap up Rcpp 0.12.18 for CRAN this weekend.