Re: [Boost-bugs] [Boost C++ Libraries] #4189: Add better support for non-default constructible function objects

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #4189: Add better support for non-default constructible function objects
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2013-08-22 04:47:17

#4189: Add better support for non-default constructible function objects
-------------------------------+--------------------------------
  Reporter:  djwalker          |      Owner:  jeffrey.hellrung
      Type:  Feature Requests  |     Status:  new
 Milestone:  Boost 1.43.0      |  Component:  iterator
   Version:  Boost 1.42.0      |   Severity:  Problem
Resolution:                    |   Keywords:  transform_iterator
-------------------------------+--------------------------------

Comment (by dave):

 As far as {{{transform_iterator}}} is concerned, there's nothing it can do
 about non-default-constructible function objects in C++03 without also
 penalizing uses of default-constructible function objects.  If there's a
 C++11 type trait that allows detection of deleted default ctors that would
 sort of let the iterator library introduce the {{{optional<F>}}} wrapper
 itself, but it wouldn't help if the default ctor was private.  My
 suggestion here would be to create a generic forwarding function object
 wrapper around {{{optional<F>}}} and use that as the function object for
 your {{{transform_iterator}}}.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/4189#comment:6>
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