Thanks for the explanation, Romain.
As a follow-up, is there a reason why value_type is defined in terms of a
reference? In the mean time, I'll use remove_reference.
-Kevin
> On Mar 31, 2015, at 1:04 AM, Romain François <rom...@r-enthusiasts.com> wrote:
>
> Hi,
>
> That’s because VTYPE::value_type is traits::r_vector_proxy<RTYPE>::type, i.e.
>
> template <int RTYPE>
> struct r_vector_proxy{
> typedef typename storage_type<RTYPE>::type& type ;
> } ;
>
> so VTYPE::value_type is int&
>
> You can either use stored_type, i.e.
>
> std::for_each( v.begin(), v.end(),[]( const VTYPE::stored_type& ) ...
>
>
> Or do a little dance with the reference qualifier:
>
> std::for_each( v.begin(), v.end(),[]( const
> std::remove_reference<VTYPE::value_type&>::type& __n ) ...
>
> Both of which are not very satisfying.
>
>
> FWIW, in Rcpp11/Rcpp14, VTYPE::value_type is defined like this:
>
> typedef typename traits::storage_type<RTYPE>::type value_type ;
>
> so IntegerVector::value_type is int, and therefore you get what you
> rightfully expect.
>
>
> Romain
>
>
>> Le 31 mars 2015 à 00:19, Kevin Thornton <krtho...@uci.edu> a écrit :
>>
>> Hi,
>>
>> I've come across an issue when compiling some code with Rcpp >= 0.11.4
>> (using R 3.1.3 with either gcc or clang on Linux, or clang on OS X).
>>
>> The code that reproduces the issue is here:
>> https://gist.github.com/molpopgen/b3bda09590172044ff84
>>
>> Specifically, the last function is where I'm running into trouble. I also
>> tried the same ideas using C++98 (function objects instead of lambda
>> expressions), and got the same results.
>>
>> The short version is that Rcpp::IntegerVector::value_type appears to lose
>> some info about value_type's const-ness when a const IntegerVector is passed
>> to an Rcpp function. I went back an tried older version of Rcpp and
>> verified that the code from the above link compiles with version from 0.11.0
>> through 0.11.3. Starting with 0.11.4, the last function in that piece of
>> code will no longer compile, and appears to think that a non-const int & is
>> the type that it is looking for.
>>
>> I tried the other STL-like typedefs that one may expect ( reference,
>> const_reference ), and they do not exist for Rcpp vector types.
>>
>> Any thoughts? Is this intended? Should I not write functions taking const
>> references to Rcpp types?
>>
>> Best,
>>
>> Kevin
>>
>> ___________________________
>> Kevin Thornton
>> Associate Professor
>> Ecology and Evolutionary Biology
>> University of California, Irvine
>> http://www.molpopgen.org
>> http://github.com/molpopgen
>> http://github.com/ThorntonLab
>>
>>
>>
>>
>>
>>
>> _______________________________________________
>> Rcpp-devel mailing list
>> Rcpp-devel@lists.r-forge.r-project.org
>> https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel
>
___________________________
Kevin Thornton
Associate Professor
Ecology and Evolutionary Biology
University of California, Irvine
http://www.molpopgen.org
http://github.com/molpopgen
http://github.com/ThorntonLab
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