[Boost-users] [MPL] unique not working?

Subject: [Boost-users] [MPL] unique not working?
From: Michael Marcin (mike.marcin_at_[hidden])
Date: 2013-10-13 23:44:22

I pass a mpl::vector with duplicates to mpl::unique and the result still 
has duplicates.
What am I doing wrong?

http://coliru.stacked-crooked.com/a/fe85b5739eb4c15f

#include <boost/mpl/vector.hpp>
#include <boost/mpl/unique.hpp>
#include <boost/mpl/equal_to.hpp>
#include <boost/mpl/placeholders.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/mpl/print.hpp>

template< typename... Args >
void test( const Args&... args )
{
     using namespace boost::mpl;
     using namespace boost::mpl::placeholders;
     typedef vector<Args...> args_types;
     typedef typename unique<args_types,
         boost::is_same<_1, _2> >::type unique_types;
     print< unique_types > x;
}

int main()
{
     int a = 0;
     char b = 0;
     test( a, b, a );
}

+ g++-4.8 -std=c++11 -O2 -Wall -pedantic -pthread main.cpp
main.cpp: In instantiation of ‘void test(const Args& ...) [with Args = 
{int, char, int}]’:
main.cpp:22:19:   required from here
main.cpp:15:27: warning: unused variable ‘x’ [-Wunused-variable]
      print< unique_types > x;
                            ^
+ ./a.out