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1 % Start with some simple facts
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2 % Note: like semantic systems, names are intrinsicly equal variables
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3 % (or variables don't exist). Names are called "atoms"
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4 likes(wallace, cheese).
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5 likes(grommit, cheese).
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6 likes(wendolene, sheep).
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7 % Each statement ends with a fullstop
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8
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9 % Rule syntax is a bit odd (":-" and "\+") but we're saying that X and Y
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10 % can be friends if X and Y like the same thing.
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11 % Poor Wendolene.
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12 friend(X, Y) :- \+(X = Y), likes(X, Z), likes(Y, Z).
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13 % "\+" is apparently logical negation (because of course it is)
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14 % so the first "subgoal" stops Wallace being Wallace's friend
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15 %
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16 % Note: Prolog nomenclature is that this is "friend/2" - friend func with 2 params |
