Re: [boost] Re: Re: Re: Re: full functoids

From: Brian McNamara (lorgon_at_[hidden])
Date: 2004-02-27 18:10:50

On Thu, Feb 26, 2004 at 03:13:11PM -0500, Brian McNamara wrote:
> On Thu, Feb 26, 2004 at 02:39:40PM +0200, Peter Dimov wrote:
> > and obvious question #2 is why I should copy the tree
> > into a list at all, when I could've just flattened it into a sequence with
> > iterators. To be fair, you do point that out yourself. 
> 
> Good point; I was just keeping the example simple.
> 
> (In fact, when you use fcpp::lists with lazy evaluation, lists
> effectively become input iterators.  It would be interesting to
> implement inorder-iterators for this tree both with and without FC++.
> Hmm.  How easy/hard would it be to build bidirectional iterators for a
> tree like this?  I've never tried.  If you have the time to cook some up
> (using Boost), I would enjoy seeing them, and comparing them to whatever I
> could cook up with FC++.)

Hmm, I wrote a reply to this, but never saw it and fear it is lost
forever in the ether.

The summary was
 - the Tree data structure I wrote is not amenable to bidirectional
   iterators (no uplinks)
 - it is reasonable to write forward iterators instead
 - you can implement forward iterators "by hand", or you can use a 
   variation of fold_tree, FC++ lists, and lazy evaluation to get 
   iterators with the same behavior (maybe with less code)

-- 
-Brian McNamara (lorgon_at_[hidden])