Re: [Boost-bugs] [Boost C++ Libraries] #8617: Surprising/wrong semantics of counting_range

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #8617: Surprising/wrong semantics of counting_range
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2014-02-21 23:25:09

#8617: Surprising/wrong semantics of counting_range
-------------------------------+------------------------
  Reporter:  pbazant@…         |      Owner:  neilgroves
      Type:  Bugs              |     Status:  assigned
 Milestone:  To Be Determined  |  Component:  range
   Version:  Boost 1.53.0      |   Severity:  Problem
Resolution:                    |   Keywords:  range
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Comment (by marc.glisse@…):

 Replying to [comment:1 nathanridge]:
 > I confess I find it surprising that an overload of counting_range() that
 takes a range exists at all.
 >
 > I agree that constructing a counting range from the first and last
 values of a range seems arbitrary, but constructing a counting range from
 the begin and end *iterator* of a range seems pointless (how would the
 resulting range be different from the original one?).

 It should be the reciprocal of {{{adaptors::indirect}}}. In a range for
 loop, there is an implicit iterator {{{iter}}} going from begin to end,
 and you get {{{*iter}}} for each element. With indirect, you get
 {{{**iter}}}. With counting_range (constructed from iterators, because the
 constructor from a range is too weird), you get {{{iter}}} (not
 dereferenced). It can be extremely useful and should be available in boost
 adaptors with the usual {{{|}}} syntax and a clearer name. This is a
 documented use of {{{counting_iterator}}}.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/8617#comment:3>
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