boolean (DfaRelation dfaRel, DfaVariableValue var, Relation relation) { DfaValue counterpart; RelationType type; if (dfaRel.leftOperand() == var) { type = dfaRel.relationType(); counterpart = dfaRel.rightOperand(); } else if (dfaRel.rightOperand() == var) { type = dfaRel.relationType().getFlipped(); counterpart = dfaRel.leftOperand(); } else { return false; } return counterpart == relation.myCounterpart && type != null; }