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Just started reading a book about AI. There is a very basic exercise but I can't figure it out, so here we go. The book is Simply Logical: Intelligent Reasoning by Example

The exercise is in the page 19.

Two stations are ‘not too far’ if they are on the same or a different line, with at most one station in between. Define rules for the predicate not_too_far.

The only rules I've seen are nearby and connected and don't know how to use this. What I've done so far is this:

not_too_far(X,Y) :- nearby(X,Y)

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    $\begingroup$ Does it say how nearby is different from connected? Where do the different lines come from? $\endgroup$ – Jaden Travnik Dec 24 '16 at 18:52
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    $\begingroup$ Let’s define two stations to be nearby if they are on the same line, with at most one station in between. And the are connected if are on the same line, and don't have any station in between. pag 18 you have the source image $\endgroup$ – ihavenokia Dec 25 '16 at 14:09
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Your intuition is good. Because "nearby" is only defined with "connected", there could only be 1 station between them. However, it says that the stations are "not_too_far" if at most one station is between them. What about if no stations are between them? If 2 stations are "connected" they should be "not_too_far" as well.

So it should be:

not_too_far(X,Y) :- connected(X,Y) ; nearby(X,Y).

Where ; denotes OR.

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    $\begingroup$ the ";" is OR? thanks $\endgroup$ – ihavenokia Dec 27 '16 at 19:28
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    $\begingroup$ Yep, look at page 18 (32 of the pdf) $\endgroup$ – Jaden Travnik Dec 27 '16 at 19:34

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