RE: Is PMT_NIL a Valid Dictionary?

[jacob]

Hi Jeff

Just to help clarify this a bit, PMT_NIL is a valid PMT object (not to be confused with null​)

PMT Dictionary type objects are nested pairs, and empty dictionary type objects (from pmt::make_dict()​ for example) are literally represented as a single PMT_NIL object under the hood, so this is specifically checked for and passes is_dict()​. As dictionary items are added, the base dictionary (or empty dict / PMT_NIL object) gets paired with added key-value pairs. Its not the best possible implementation, but has served GR for some time. PMTs are getting a modernization / overhaul soon.

The is_pdu() check should abstract that oddness a bit.

Jacob

------- Original Message -------
On Thursday, June 30th, 2022 at 7:12 AM, Jeff S <e070832@hotmail.com> wrote:

Cool.  I appreciate the clarification.  I had always taken an empty dictionary as a dictionary object without data, and a NIL as not an object, and the two were different.  This helps my PDU checking.

 

And I also found the update I missed which added is_pdu(), which simplifies some of my checking.  So, even better!

 

Thanks for the help,

Jeff

 

From: Jeff Long <willcode4@gmail.com>
Sent: Thursday, June 30, 2022 8:02 AM
To: Jeff S <e070832@hotmail.com>
Cc: discuss-gnuradio@gnu.org
Subject: Re: Is PMT_NIL a Valid Dictionary?

 

Yes, an empty dict is NIL, so that is (confusingly) valid.

 

On Thu, Jun 30, 2022 at 7:05 AM Jeff S <e070832@hotmail.com> wrote:

GNU Radio Version:  v3.9.6.0-23-ge3506b13

 

I was writing a QA test and decided to try,

 

self.assertTrue(pmt.is_dict(pmt.PMT_NIL))

 

and it passes.  I was just wondering if pmt.PMT_NIL is considered a valid dictionary object, as opposed to,

 

my_dict = pmt.make_dict()

self.assertTrue(pmt.is_dict(my_dict))

 

Just trying to get a better understanding and couldn’t find an answer.

 

Regards,

Jeff