# Re: Questions on callback functions implementation of blocks in gr-trellis

**URL:** <https://www.ruby-forum.com/t/re-questions-on-callback-functions-implementation-of-blocks-in-gr-trellis/240866>\
**Category:** GNU Radio\
**Created:** [May 4, 2014, 3:18am UTC](https://www.ruby-forum.com/t/re-questions-on-callback-functions-implementation-of-blocks-in-gr-trellis/240866 "2014-05-04T03:18:10Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Detlef\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/58f4c7/32.png) [@Detlef\_R](https://www.ruby-forum.com/u/Detlef_R)\
**Post date:** [May 4, 2014, 3:18am UTC](https://www.ruby-forum.com/t/re-questions-on-callback-functions-implementation-of-blocks-in-gr-trellis/240866/1 "2014-05-04T03:18:10Z")

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Zhe,

there are way too many changes in this diff file for anyone to track and  
debug.

I suggest you start with a clean gr-trellis and change JUST one block  
(say  
the viterbi\_combined)  
and see if this change propagates in python and grc as you expect.  
You can also post this change to the list for further feedback (together  
with the SIMPLEST possible grc example  
that indicates the problem.)

best,  
Achilleas