Re: [Boost-users] boost::range RangeConcept problem.

On Thu, Jan 17, 2013 at 5:25 AM, Jeffrey Lee Hellrung, Jr. < jeffrey.hellrung@gmail.com> wrote:

On Tue, Jan 15, 2013 at 10:26 AM, Hurcan Solter wrote:

...

The following snippet is the mock-up of the problem I am having in order to be able to reproduce.

-------------------------------------------------------------------------------- #include <iostream> #include #include #include #include #include

using namespace boost::assign; struct wxSize { wxSize(int height=0,int width=0):m_height(height),m_width(width) { } int GetWidth() const {return m_width;} int m_height; int m_width; }; class wxWindowBase { public: wxSize GetTextExtent(const std::string val) { return wxSize(0,val.length()); } void DoLayout(std::vectorstd::string m_FilteredItems) {

using boost::adaptors::transformed; wxSize longest = *boost::max_element(m_FilteredItems | transformed(boost::bind(&wxWindowBase::GetTextExtent,this,_1)),

boost::bind(std::less<int>(),boost::bind(&wxSize::GetWidth,_1),boost::bind(&wxSize::GetWidth,_2)));

std::cout <std::string input; input += "o","two","threexxx","four"; wxWindowBase window; window.DoLayout(input); }

----------------------------------------------------------------------------------------- The above code fails to compile on GCC4.7.2 and MSVC10 although it compiles and runs fine on clang3.3

From what I understand ,transformed returns a Single Pass Range and max_element expects a ForwardRange and that's the gist of the problem.But it works for something like

max_element(someint_vector | transformed(doubleit()),std::less<int>()); without problems.

Is there a elegant way to achieve what I am trying to without using a intermediate container? Thanks in advance..

I would try simplifying things (e.g., replace the uses of bind with explicit function objects; define an operator< for wxSize), then if you're still lost, paste the error (I don't have immediate access to MSVC 10 or gcc 4.7).

- Jeff

I am pretty convinced that Akira has nailed it. The problem was in the first line and in any case it does not make sense defining operator < for size objects unless you are comparing areas and as for functors I've used bind exclusively to avoid writing them (hence the std::less) .

Seeing that it compiles fine on clang I've disabled concept checks by defining BOOST_RANGE_ENABLE_CONCEPT_ASSERT 0 . Apparently clang bypasses concept check or maybe it's disabled for that particular compiler (Is it?) . It works fine on both MSVC and gcc now. Although I might be shooting myself in the foot

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