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CHR/chr/examples/scheduling.pl

@@ -0,0 +1,64 @@
+% 980312 Thom Fruehwirth, LMU
+
+:- use_module(library(chr)).
+
+handler scheduling.
+
+option(check_guard_bindings, on).
+
+constraints leq/2, optimize/0.
+% leq(X+N,Y) means: task X starts at least N time units before task Y
+
+% assumes leq-relation is non-circular
+
+redundant @ leq(N,Y), leq(M,Y) <=> M=<N | leq(N,Y).
+
+% optimize gives smallest possible value to a variable
+
+optimize @  optimize#Id \ leq(X,Y) <=> 
+	ground(X),var(Y),findall_constraints(Y,leq(_,Y),L),L=[]
+        | 
+	Y is X 
+        pragma passive(Id).
+
+% classical example --------------------------------------
+	
+build_house([Start,A,B,C,D,E,F,G,H,I,J,End]) :-
+	leq(Start+0,A),
+	leq(A+7,B),
+	leq(A+7,D),
+	leq(B+3,C),
+	leq(C+1,E),
+	leq(D+8,E),
+	leq(C+1,G),
+	leq(D+8,G),
+	leq(D+8,F),
+	leq(C+1,F),
+	leq(F+1,H),
+	leq(H+3,I),
+	leq(G+1,J),
+	leq(E+2,J),
+	leq(I+2,J),
+	leq(J+1,End),
+	optimize,
+	Start=0.	
+
+/*
+| ?- build_house([Start,A,B,C,D,E,F,G,H,I,J,End]).
+
+A = 0,
+B = 7,
+C = 10,
+D = 7,
+E = 15,
+F = 15,
+G = 15,
+H = 16,
+I = 19,
+J = 21,
+End = 22,
+Start = 0,
+optimize ? 
+*/
+	
+% end of handler scheduling