[boost] Re: Re: Re: Zero Unnecessary Temporary Objects: A Revolution

From: Samuel Krempp (krempp_at_[hidden])
Date: 2002-10-17 11:02:16

le Dimanche 13 Octobre 2002 18:59, tslettebo_at_[hidden] écrivit :

> As pointed out in another posting, as I understand, the only thing you can
> safely do with an end() iterator is to compare it with other iterators.
> Without this guarantee, it would limit how you could implement the end()
> iterator. See my other posting with the tree-iterators for an example. How
> would you implement operator--() on that end() iterator?

Well, schematically, the tree iterator I wrote keep a pointer to the root 
of the tree from which it came, plus a 'current node' pointer that is set 
to NULL for end().
then calling -- on an end pointer does :
.go to root
.{go down, and to your right, as much as you can }

it's very similar to what you do in ++begin() for an In-order iteration. 
And even in post-order, when at a node on the bottom, calling ++  might 
lead to more internal node iterations than --end() 
(as you need to first go up. possibly up to root).

All in all I don't see tree iterators as an argument to disallow --end().

-- 
Samuel