--- pl:prolog:pllib:acyclic_path_2 [2019/06/27 15:50]
+++ pl:prolog:pllib:acyclic_path_2 [2019/06/27 15:50] (aktualna)
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+====== Acyclic path 2 ======
+{{tag>graphs operators}}
+===== Description =====
+Path-finding in a graph, acyclic path with cost
+**Source**:  PROLOG programming for artificial intelligence, 3rd Edition, Harlow, 2001, ISBN 0-201-40375-7.
+===== Download =====
+Program source code: {{prolog:pllib:acyclic_path_2.pl}}
+===== Listing =====
+<code prolog>
+% Figure 9.21   Path-finding in a graph:  Path is
+% an acyclic path with cost Cost from A to Z in Graph.
+:- op( 900, fy, not).
+% path( A, Z, Graph, Path, Cost):
+%    Path is an acyclic path with cost Cost from A to Z in Graph
+path( A, Z, Graph, Path, Cost)  :-
+  path1( A, [Z], 0, Graph, Path, Cost).
+path1( A, [A | Path1], Cost1, Graph, [A | Path1], Cost1).
+path1( A, [Y | Path1], Cost1, Graph, Path, Cost)  :-
+   adjacent( X, Y, CostXY, Graph),
+   not member( X, Path1),
+   Cost2 is Cost1 + CostXY,
+   path1( A, [X, Y | Path1], Cost2, Graph, Path, Cost).
+% not Goal): negation as failure;
+%   Note: This is often available as a built-in predicate,
+%   often written as prefix operator "\+", e.g. \+ likes(mary,snakes)
+not Goal  :-
+  Goal, !, fail
+  ;
+  true.
+</code>
+===== Comments =====

pl/prolog/pllib/acyclic_path_2.txt · ostatnio zmienione: 2019/06/27 15:50 (edycja zewnętrzna)

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