Re: List container: Insert and Delete

[Darren New <dnew@san.rr.com>]

Ted Dennison wrote:
> >For example, I strongly suggest that there be a mechanism to translate
> >between positions and integer offsets and back. This is an O(N)
> >operation, obviously, compared to the O(1) of moving the position.
> 
> You had me, before you presented this example. :-)

I don't follow. What's unreasonable about the example? It seems like a
perfectly reasonable way of saying "does this come before that in the
list", or saving positions to a stream, or printing something out for
debugging, or whatever.

Saying "we're not going to implement this operation because it's
inefficient" doesn't sound like a good idea to me, is all.

> >Then you need some way to map a "pos" onto something you can save, and
> >something to map it back. For example, if you're implementing Streams,
> >you'll need something like this anyway, yes?

> If you are implementing them for positions, which we currently are not (check
> the spec). That could just be an oversight, though.

Someone will want to save positions. There's three choices: implement
positions for streams, provide ways to convert to something simpler
(like Integer), or force the person who wants that to keep track of the
integer as well as the position or to implement the run-through-the-list
somehow (assuming positions have equality defined to start with). I vote
for anything except the latter. It would be nice to be able to be able
to print out the indicies and values of a list for debugging, however.


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Darren New 
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