Re: [Discuss-gnuradio] GRC taps as parameter in hierarchical block?

[Koslowski, Sebastian (CEL)]

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On 03/19/2015 04:26 PM, Tom Rondeau wrote:
> In the meantime, perhaps using parameters to define other parameters isn't 
> really the right thing to
do, anyways. You are setting the default value based on the default
value of another parameter. When actually using the hier_block in
another flowgraph, that nfilts doesn't propagate through to reset the
default value of the taps parameter. So I don't think that this would
even have the desired behavior you're looking for.

GRC evaluates params in a separate namespace which is then merged with
the one holding variables and imports. While it is trivial to change
that, I must cite with Tom, params should not depend on each other.
However, your taps param should have been marked invalid.

If I understand your scenario correctly you could try one these (no
warranty):

- - if all you need is a default set of taps, use "taps or default_taps"
in your filter block and set the taps param default to "()"
- - pass a filter generator function into the block. Using
functools.partial you even preset (some) args (and standardize the call
signature) in the parent fg and then call it in the filter block
"taps_generator(param1, param2)"
- - pass the filter design call as a string and eval it. (Ugly)

Sebastian

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