Re: [Boost-users] [ptr_container] Transferring the Last Element from a ptr_vector

Subject: Re: [Boost-users] [ptr_container] Transferring the Last Element from a ptr_vector
From: Sebastian Theophil (stheophil_at_[hidden])
Date: 2009-09-09 12:52:13

> Um -- I'm under the impression that decrementing the iterator returned
> by end() is discouraged. There are containers for which that
definitely
> would not work.
> 
> I'm guessing that he would recommend something like
> other->geneVect.rbegin().base() instead -- presuming you've already
> ensured that other->geneVect isn't empty.

Nat,

you would be half right only if GeneVectType::iterator were a
forward_iterator, but a ptr_sequence_adapter is always reversible, so
the iterator must be bidirectional.

Internally, the boost::reverse_iterator you propose also has to
decrement, so it doesn't work any better. Additionally, your proposed
solution crashes because other->geneVect.rbegin().base() returns in fact
other->geneVect.end(). Only *other->geneVect.rbegin() returns
*(other->geneVect.end()-1).

Regards
Sebastian

--
Sebastian Theophil . stheophil_at_[hidden]
Software Engineer
 
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