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DonaldKellett/lpn-3-practical-4.pl

Created December 22, 2018 09:00
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Learn Prolog Now! - Chapter 3 - Practical Session - Programming Exercise 4 - Modes of Transportation
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lpn-3-practical-4.pl
% Knowledge base of travel routes (provided)
% Assumption: these routes are unidirectional
byCar(auckland,hamilton).
byCar(hamilton,raglan).
byCar(valmont,saarbruecken).
byCar(valmont,metz).
byTrain(metz,frankfurt).
byTrain(saarbruecken,frankfurt).
byTrain(metz,paris).
byTrain(saarbruecken,paris).
byPlane(frankfurt,bangkok).
byPlane(frankfurt,singapore).
byPlane(paris,losAngeles).
byPlane(bangkok,auckland).
byPlane(singapore,auckland).
byPlane(losAngeles,auckland).
% travel/3 - In order to travel from X to Y, what route(s) and mode(s) of transportation Z should we take?
travel(X, Y, byCar(X, Y)) :- byCar(X, Y).
travel(X, Y, byTrain(X, Y)) :- byTrain(X, Y).
travel(X, Y, byPlane(X, Y)) :- byPlane(X, Y).
travel(X, Y, byCar(X, Z, P)) :- byCar(X, Z), travel(Z, Y, P).
travel(X, Y, byTrain(X, Z, P)) :- byTrain(X, Z), travel(Z, Y, P).
travel(X, Y, byPlane(X, Z, P)) :- byPlane(X, Z), travel(Z, Y, P).
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