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Re: Continuations with pictures
See the movie _Memento_!
Not only is a great film, but, apparently, it will teach you about
continuations as well.
On Friday, August 8, 2003, at 11:05 AM, Kimberley Burchett wrote:
> On Fri, 8 Aug 2003, Kevin Kelleher wrote:
>> So here is a picture -- maybe you can tell me what's wrong
>> with it:
> It seems like you're thinking of all the junk in the room as being
> part of
> the continuation. But it would probably be more appropriate to think
> the junk as global variables, that would still be wherever they were
> after you invoked the continuation...
> I think it would be easier to offer a slightly different picture rather
> than try to fix up bit by bit the one that you illustrated.
> A continuation is more like a little envelope containing instructions
> about what to do next.
> Imagine that right after your daughter cleaned up her room, she wanted
> go get some ice cream as a reward. She knows that she's prone to
> these things so she decides to write a note to remind herself (yes,
> very odd for a child to not only forget the reward, but also have the
> foresight to write it down, but bear with me). On the outside of the
> envelope, she writes "Do this next".
> Now her friends come over, and her room gets messed up again. Time
> The next morning, she wakes up and in the midst of the mess, she
> an envelope labeled "Do this next". She opens it, and it tells her to
> get ice cream. She thinks this sounds like a good idea, so she does.
> Notice that she didn't put the room back in order first. The room is
> the global variables -- nothing happens to them simply by invoking the
> continuation. Basically, you can think of the continuation as a
> "train of
> thought". When she wrote down the note (created the continuation), she
> had intended to get ice cream. She then promptly forgot this plan, so
> that train of thought disappeared. But then she read the note (invoked
> the continuation) and the train of thought was resumed. Notice also
> the original motivation for getting ice cream was as a reward for
> cleaned up the room -- but the fact that the room is now messed up
> doesn't prevent her from getting ice cream anyway.
> The label on the envelope is arbitrary -- it's simply the name of the
> variable that holds the continuation. You could label it anything you
> wanted, but it would still have the effect of changing your train of
> There's no such thing as a future continuation, since nobody has yet
> that train of thought, so they can't write it down. There is a
> between upward and downward continuations, but the difference is
> mostly a
> matter of implementation and how you use them.
> I didn't address all the issues involved in continuations -- e.g. where
> they "return to", but I think this conveys the gist of the concept at
> same level that you were originally asking about.
> Kimberley Burchett