| 1 | #!/usr/bin/env swipl -s
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| 2 |
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| 3 | /*
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| 4 | * Rick van der Zwet
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| 5 | * 0433373
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| 6 | * Prolog programming assigment 1
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| 7 | * Licence: BSD
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| 8 | * $Id: assignment1.pro 299 2007-11-08 00:10:31Z rick $
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| 9 | */
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| 10 |
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| 11 | /* final call, [X,Y] member of Graph */
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| 12 | trans_dag(X, Y, Graph) :-
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| 13 | member([X,Y], Graph).
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| 14 |
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| 15 | /* Find all nodes which are findable from X */
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| 16 | trans_dag(X, Y, Graph) :-
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| 17 | member([X,Z], Graph),
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| 18 | trans_dag(Z, Y, Graph).
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| 19 |
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| 20 | /* final call, [X,Y] member of Graph, do note initial path is set []
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| 21 | * over here */
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| 22 | trans(X, Y, Graph, _, []) :-
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| 23 | member([X,Y], Graph).
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| 24 |
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| 25 | /* Find all nodes which are findable from X, but where
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| 26 | * passed node is not member of Avoid, to avoid cycles
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| 27 | * Path is constructed just the other way around
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| 28 | */
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| 29 | trans(X, Y, Graph, Avoid, Path) :-
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| 30 | not(member(X, Avoid)),
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| 31 | member([X,Z], Graph),
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| 32 | Path=[Z|PathTail],
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| 33 | AvoidAdded=[X|Avoid],
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| 34 | trans(Z, Y, Graph, AvoidAdded, PathTail).
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| 35 |
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| 36 | /* init trans to trans 'system' call, which just ignored the Path and
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| 37 | * makes the Avoid list starting []
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| 38 | */
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| 39 | trans(X, Y, Graph) :-
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| 40 | trans(X, Y, Graph, [], _).
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| 41 |
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| 42 |
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| 43 | /* init trans to path 'system' call
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| 44 | * makes the Avoid list starting []
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| 45 | */
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| 46 | path(X, Y, Graph, Path) :-
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| 47 | trans(X, Y, Graph, [], Path).
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