[boost] Re: Collection concept

From: Greg Colvin (gcolvin_at_[hidden])
Date: 2000-01-12 14:53:57

I have also not been following this thread, but I agree with
Howard's take below.  So if you are trying to state general
container requirements for proxied containers you will need
to look at all the algorithms.

----- Original Message ----- 
From: Howard Hinnant <hinnant_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Wednesday, January 12, 2000 7:52 AM
Subject: [boost] Re: Collection concept

> Dave Abrahams wrote on 1/11/2000 8:07 PM
> >Also, I would particularly like to hear from Howard and Greg on this, since
> >they have both had experience with proxied containers. Does this reflect the
> >intended concept, or would it be acceptable for member access to fail for
> >references?
> 
> I haven't been following this thread.  But as my 0.02 has been requested, 
> I'll give it.  Be forewarned that it may be way out in left field. :-)
> 
> I gave my thoughts on proxied container requirements in another thread 
> and I'll repeat it here.  I chose to link the container requirement with 
> the algorithm and vice-versa:
> 
> >So at least for me, one requirement of a proxied iterator is that it 
> >offer a specialization of any method that the algorithm must call with a 
> >T& (e.g. sort requires swap(iter, iter)).  And a requirement on the 
> >algorithm is that it not call anything taking a T& except for those 
> >methods that the proxied iterator are required to specialize.
> 
> This is result of my experience with vector<bool>.  I don't have 
> extensive experience with proxied containers other than this one.  But 
> the point is, if I'm wanting to sort a vector<bool>, I don't give a flip 
> if I can call flip on a reference. ;-)  All I care about is that I can 
> call swap on two references.  So I require:
> 
> static void swap(reference x, reference y);
> 
> If the proxy has this, then the container is useful to me.  If it 
> doesn't, then it is not.
> 
> Naturally my requirements for being useful are going to vary with 
> different algorithms.
> 
> So I don't know how you would word it, but the bottom line is that the 
> proxied container is useful if it works with the algorithm you want to 
> use it with.  And that can involve more than just the implementation of 
> member functions in the proxy class.  And the proxy need not completely 
> duplicate the functionality of an actual reference to be useful for a 
> given algorithm.
> 
> -Howard
> 
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