## Re: [aima-talk] search/domain/vacuum.lisp source code "rotate" function

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• The theory is vector arithmetic. If you work out the combinations, it turns out the same as what you would be doing in your enumeration of cases. -Peter
Message 1 of 2 , Dec 1, 2003
The theory is vector arithmetic. If you work out the combinations, it
turns out the same as what you would be doing in your enumeration of
cases.

-Peter Norvig

On Sunday, November 30, 2003, at 06:33 PM, chenyu468 wrote:

> Hi everyone,
> I have read "vacuum.lisp", "utility.lisp" source code. The
> function "rotate" in the "utility.lisp" make me puzzle.
>
> The purpose of "rotate" function is to change the "oriention" of
> vacuum depends on the "current orientation" and "change requirement,
> for example 'left', 'right'".
>
> If I wrote this function ("rotate"), I would use the enumeration
> method to solve the problem, that's, combination of 4 possible ((1 0)
> (-1 0) (0 1) (0 -1))orientation and 2 possible change ("left"
> or "right").
>
> But the author ( Mr.Norvig or Mr. Russel) has solve the problem by
> algebra operation which is more elegant and abstract (just 2 possible
> combination, not 8 possible combination). I like this method, but
> don't know what's the theory details behind it. What's it, could you
> help me?
>
> Thank you for your attention.
> kind regards/chenyu
>
>
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