Error: Unable to stratify relation(s) {chosen,diffchoice}
Relation diffchoice in file choice.dl at line 16
.decl diffchoice(s:Integer, p:Integer)
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has cyclic negation in file choice.dl at line 25
chosen(s, p) :- student(s, m, _), professor(p, m), !diffchoice(s, p).
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1 errors generated, evaluation aborted
