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!7

/*
    Event 1 happens before event 2 :=
      vars {event 1, event 2, X, Y}
      Event 1 happens at day X.
      Event 2 happens at day Y.
      X < Y.

*/

sclass Obj {
  class Fact {}
  
  class StatementsWithVars {
    L<Fact> statements;
    Set<Var> vars;
    
    *() {}
    *(Fact... statements) {
      statements = asList(statements);
      collectVars();
    }
    
    void collectVars {
      vars = new Set;
      fOr (Fact f : statements)
        vars.addAll(print("Vars", findVars(statement)));
    }
  }
  
  L<Var> findVars(Fact statement) {
    Cl out = transitiveHullOfFunction
      nonStaticNonPrimitiveNonTransientFieldValues(statement);
    print(classNames(out));
    ret instancesOf Var(out);
  }
  
  record $HappensBefore$<A, B>(A event1, B event2) extends Fact {}
  record $HappensAtDay$<A, B>(A event, B y) extends Fact {}
  record $LessThan$<A, B>(A x, A y) extends Fact {}
  
  // Enrolling happens before graduation.
  // Enrolling happens at day 200.
  // Graduation happens at day 100. // Contradiction!
  
  L<Fact> facts = ll(
    new $HappensBefore$("enrolling", "graduation"),
    new $HappensAtDay$("enrolling", 200),
    new $HappensAtDay$("graduation", 200)
  );
  
  void rule1($HappensBefore$ in) {
    O event1 = in.event1, event2 = in.event2;
    Var X = new("X"), Y = new("Y");
    emit(new StatementsWithVars(
      $HappensAtDay$(event1, X),
      $HappensAtDay$(event2, Y),
      $LessThan$(X, Y)
    ));
  }

  *() {
    pnlWithHeading("Facts", facts);
  }
}

p-exp { new Obj; }