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pl:prolog:pllib:breadth-first_search [2019/06/27 15:50] (aktualna)
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 +====== Breadth-first search ======
 +{{tag>​searching}}
 +===== Description =====
 +An implementation of breadth-first search.
 +
 +**Source**: ​ PROLOG programming for artificial intelligence,​ 3rd Edition, Harlow, 2001, ISBN 0-201-40375-7.
 +===== Download =====
 +Program source code: {{breadth-first_search.pl}}
 +===== Listing =====
 +<code prolog>
 +% Figure 11.10   An implementation of breadth-first search.
 +
 +:- op( 900, fy, not).
 +
 +% 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.
 +
 +% solve( Start, Solution):
 +%    Solution is a path (in reverse order) from Start to a goal
 +
 +solve( Start, Solution) ​ :-
 +  breadthfirst( [ [Start] ], Solution).
 +
 +% breadthfirst( [ Path1, Path2, ...], Solution):
 +%   ​Solution is an extension to a goal of one of paths
 +
 +breadthfirst( [ [Node | Path] | _], [Node | Path]) ​ :-
 +  goal( Node).
 +
 +breadthfirst( [Path | Paths], Solution) ​ :-
 +  extend( Path, NewPaths),
 +  conc( Paths, NewPaths, Paths1),
 +  breadthfirst( Paths1, Solution).
 +
 +extend( [Node | Path], NewPaths) ​ :-
 +  bagof( [NewNode, Node | Path],
 +         ( s( Node, NewNode), not member( NewNode, [Node | Path] ) ),
 +         ​NewPaths),​
 +  !.
 +
 +extend( Path, [] ).              % bagof failed: Node has no successor
 +</​code>​
 +===== Comments =====
  
pl/prolog/pllib/breadth-first_search.txt · ostatnio zmienione: 2019/06/27 15:50 (edycja zewnętrzna)
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