id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
9515	[range] uniqued adaptor (and hence adjacent_filtered) returns wrong elements	Eric Niebler	Neil Groves	"The following shows the difference between the `boost::range::unique_copy` algorithm and the `boost::adaptors::unique` adaptor.

{{{
#include <string>
#include <vector>
#include <iterator>
#include <iostream>
#include <boost/algorithm/string.hpp>
#include <boost/range/algorithm/copy.hpp>
#include <boost/range/algorithm/unique_copy.hpp>
#include <boost/range/adaptor/uniqued.hpp>

struct istring
{
    char const *c_str;
    istring(char const *s) : c_str(s) {}
    bool operator==(istring u) const
    {
        return boost::iequals(c_str, u.c_str);
    }
    friend std::ostream& operator<<(std::ostream& sout, istring s)
    {
        return sout << s.c_str;
    }
};

int main()
{
    std::vector<istring> strs;
    strs.push_back(istring(""hello""));
    strs.push_back(istring(""HELLO""));
    std::cout << ""boost.range: \n"";
    boost::range::copy(
        boost::adaptors::unique(strs),
        std::ostream_iterator<istring>(std::cout));

    std::cout << ""\n"";
    std::cout << ""std algo: \n"";
    boost::range::unique_copy(strs,
        std::ostream_iterator<istring>(std::cout));
    std::cout << ""\n"";
}
}}}

This prints:

{{{
boost.range:
HELLO
std algo:
hello
}}}

`std::unique` and `std::unique_copy` yield the *first* element in a sequence of equivalent elements. The Boost adaptor yields the last. This is an important and observable difference.

Since `uniqued` is implemented in terms of `adjacent_filtered`, the problem needs to be fixed there.
"	Bugs	closed	To Be Determined	range	Boost 1.54.0	Problem	fixed