public static void updatePropositionTruthValue(Proposition self, Keyword updatemode) {
    if (updatemode == Logic.KWD_ASSERT_TRUE) {
      Proposition.assignTruthValue(self, Stella.TRUE_WRAPPER);
    }
    else if (updatemode == Logic.KWD_ASSERT_FALSE) {
      Proposition.assignTruthValue(self, Stella.FALSE_WRAPPER);
    }
    else if (updatemode == Logic.KWD_PRESUME_TRUE) {
      Proposition.assignTruthValue(self, Logic.DEFAULT_TRUE_TRUTH_VALUE);
    }
    else if (updatemode == Logic.KWD_PRESUME_FALSE) {
      Proposition.assignTruthValue(self, Logic.DEFAULT_FALSE_TRUTH_VALUE);
    }
    else if (updatemode == Logic.KWD_RETRACT_TRUE) {
      if (Proposition.trueP(self) &&
          (!(self.kind == Logic.KWD_FUNCTION))) {
        Proposition.deassignTruthValue(self, updatemode);
      }
    }
    else if (updatemode == Logic.KWD_RETRACT_FALSE) {
      if (Proposition.falseP(self)) {
        Proposition.deassignTruthValue(self, updatemode);
      }
    }
    else if (updatemode == Logic.KWD_CONCEIVE) {
    }
    else {
      { OutputStringStream stream000 = OutputStringStream.newOutputStringStream();

        stream000.nativeStream.print("`" + updatemode + "' is not a valid case option");
        throw ((StellaException)(StellaException.newStellaException(stream000.theStringReader()).fillInStackTrace()));
      }
    }
    Proposition.runUpdatePropositionDemon(self, updatemode);
  }