Remove algo logic duplication Round 3

[Marc Glisse]

On Sun, 29 Sep 2013, Paolo Carlini wrote:

>> Maybe we could use more references? The user-facing functions have to 
>> take iterators by value, but I think the inline helpers could use 
>> references.
>
> Marc it would be great if you could prepare a patch or provide (offline 
> too, if you like) detailed guidance to Francois. We really want this 
> change to be safe and nop (or very close to that) from the performance 
> point of view. That's why I remained unconvinced and hesitant for such a 
> long time. If we are not sure, let's just admit it, give the issue more 
> thought and reconsider a more satisfactory patch for the next release 
> series.

Busy now, but please don't revert the patch because of my post. The number 
of copies in the previous code was already rather large, showing that we 
didn't care about it. The new code increases it a bit, but only by a 
constant factor. We can improve that incrementally, I believe.

-- 
Marc Glisse