--- pl:prolog:pllib:dutch_flag [2019/06/27 15:50]
+++ pl:prolog:pllib:dutch_flag [2019/06/27 15:50] (aktualna)
@@ Linia 1: / Linia 1: @@
+====== Dutch flag ======
+{{tag>problem_solving}}
+===== Description =====
+A solution to the Dutch flag problem
+**Source**:  The Art of Prolog
+===== Download =====
+Program source code: {{dutch_flag.pl}}
+===== Listing =====
+<code prolog>
+/*
+    dutch(Xs,RedsWhitesBlues) :-
+	RedsWhitesBlues is a list of elements of Xs ordered
+	by color: red, then white, then blue.
+*/
+	dutch(Xs,RedsWhitesBlues) :-
+		distribute(Xs,Reds,Whites,Blues),
+		append(Whites,Blues,WhitesBlues),
+		append(Reds,WhitesBlues,RedsWhitesBlues).
+/*
+    distribute(Xs,Reds,Whites,Blues) :-
+	Reds, Whites, and Blues are the lists of red, white,
+	and blue elements in Xs, respectively.
+*/
+	distribute([red(X)|Xs],[red(X)|Reds],Whites,Blues) :-
+		distribute(Xs,Reds,Whites,Blues).
+	distribute([white(X)|Xs],Reds,[white(X)|Whites],Blues) :-
+		distribute(Xs,Reds,Whites,Blues).
+	distribute([blue(X)|Xs],Reds,Whites,[blue(X)|Blues]) :-
+		distribute(Xs,Reds,Whites,Blues).
+	distribute([],[],[],[]).
+%	Program 15.5: A solution to the Dutch flag problem
+</code>
+===== Comments =====

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

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