@Override public <R, C> R accept(Visitor<R, C> visitor) { return visitor.visitVariableExp(this); }
@Override public <R, C> R accept(Visitor<R, C> visitor) { return visitor.visitOperationCallExp(this); }
@Override public <R, C> R accept(Visitor<R, C> visitor) { return visitor.visitCollectionLiteralExp(this); }