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// Tower of Hanoi Puzzle
// Rules
hanoi(return, source, target, aux) >< (int n)
| n==0 =>
// Erase the source, target and aux
source ~ Eraser,
target ~ Eraser,
aux ~ Eraser,
// result
return~[]
| _ =>
// Duplicate the source, target and aux
source ~ Dup(src1, Dup(src2, src3)),
target ~ Dup(tgt1, Dup(tgt2, tgt3)),
aux ~ Dup(aux1, aux2),
// recursive applications
hanoi(ret1, src1, aux1, tgt1)~(n-1),
hanoi(ret2, aux2, tgt2, src2)~(n-1),
// result
return << Append(ret1, (n,src3,tgt3):ret2);
// Net
hanoi(result, A, C, B) ~ 3;
result; // should be [(1,A,C),(2,A,B),(1,C,B),(3,A,C),(1,B,A),(2,B,C),(1,A,C)]
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