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Re: [Discuss-gnuradio] Python pass parameter as const *gr_complex?


From: Ludwig Stephan (CR/AEH4)
Subject: Re: [Discuss-gnuradio] Python pass parameter as const *gr_complex?
Date: Wed, 21 Jan 2015 15:26:37 +0000

Hi Tom,

 

thank you for clarification. The problem arose, when I wanted to use the method from within a *python*block’s  work function. But I understood, that this is not possible (a.t.m.), and I will write a C++ clock, which should perform better anyways ;-)

 

Best regards

Stephan Ludwig

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Von: address@hidden [mailto:address@hidden Im Auftrag von Tom Rondeau
Gesendet: Mittwoch, 21. Januar 2015 14:50
An: Ludwig Stephan (CR/AEH4)
Cc: address@hidden
Betreff: Re: [Discuss-gnuradio] Python pass parameter as const *gr_complex?

 

On Wed, Jan 21, 2015 at 3:13 AM, Ludwig Stephan (CR/AEH4) <address@hidden> wrote:

Thank you, Tom, for your enlightening answer. Please let me ask two additional questions:

1) If I understood your explanation correctly, as a consequence of this, one could not use the decision_maker method within a block, which is coded solely in python. Right?

 

Correct.

 

2) Isn't "const gr_complex*" a type, which is used very often in the block I/O interfaces, and shouldn't, thus, the GR configuration of SWIG already let it know how to translate python/complex to gr_complex?

 

No. That type is almost never used. What is often used is "const std::vector<gr_complex>". But again, this class was designed to be called from within a block's work function, so the data structure would have already been a "const gr_complex*" (casting the input_items argument).

 

Tom

 

 


Best regards

Stephan Ludwig

Robert Bosch GmbH
Corporate Sector Research & Advance Engineering, Communication Technology (CR/AEH4)
Renningen
70465 Stuttgart
GERMANY
www.bosch.com

Tel. +49(711)811-8809
Fax +49(711)811-1052
Mobile +49(172)5630639
address@hidden

Registered Office: Stuttgart, Registration Court: Amtsgericht Stuttgart, HRB 14000;
Chairman of the Supervisory Board: Franz Fehrenbach; Managing Directors: Dr. Volkmar Denner,
Dr. Stefan Asenkerschbaumer, Dr. Rolf Bulander, Dr. Stefan Hartung, Dr. Dirk Hoheisel, Christoph Kübel,
Uwe Raschke, Wolf-Henning Scheider, Dr. Werner Struth, Peter Tyroller
Von: address@hidden [mailto:address@hidden] Im Auftrag von Tom Rondeau
Gesendet: Dienstag, 20. Januar 2015 15:57
An: Ludwig Stephan (CR/AEH4)
Cc: address@hidden
Betreff: Re: [Discuss-gnuradio] Python pass parameter as const *gr_complex?


On Wed, Jan 7, 2015 at 7:57 AM, Ludwig Stephan (CR/AEH4) <address@hidden> wrote:
Hi list,
 
I am trying to use the gr::digital::constellation::decision_maker(.) method from python, but I get an error message.
In order to reproduce call in python:
 
import gnuradio.digital
a = gnuradio.digital.constellation_qpsk()
b = complex(1+1j)
a.decision_maker(b)
=> TypeError [..] argument 2 of type ‘gr_complex const*’
The C++-implementation is wrapped by SWIG, where the error occurs.
 
This might be a silly question, but what am I doing wrong?
 
Thanks for any help.
 
Best regards
 
Stephan Ludwig

Hi Stephan,

You're not doing anything wrong per se, but the block isn't really meant to be used that way. SWIG needs to be told how to handle some types of argument formats, and it hasn't been told how to handle this one.

The post 3.7 way we've been handling SWIG is to just include the public .h file as the interface, so all methods are exported into SWIG. A class like this needs that method to be public for use as a contained object in the block that calls it, but it's not really meant for use outside like this. Not that it couldn't be, but you'd have to work with SWIG to let it understand how to call that function with the proper input type.

Tom

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