[Discuss-gnuradio] trig function in grc variable

[d.des]

I want to add a phase shift block to a grc flowgraph that is controlled
by a scrollbar. Searching for "phase shift block" returns several
suggestions from several years ago to use the "Multiply Const" block
with the argument: "math.cos(angle), math.sin(angle)" in the "const"
field. If I try that I get the error:

Expression None is invalid for type 'complex'.

I can enter fixed complex variables or references to other variables or
parameters, I just can't do trig functions. I'm currently using the
equation: "pow(10,snr/20.)" in a Noise Source block and it understands
that just fine. Is there a way to do trig functions in a block field? 

I'm currently using a clean install and build of gnuradio retrieved
from git a few days ago, but this issue has been the case for the
several versions I've retrieved and built over the past year or so. I
ended up building a hier block with complex_to_magphase, add constant,
and the magphase_to_complex but that seems very inefficient. The
transcendental function seems to be oriented to streams rather than
constants that rarely change. I also considered an OOT block but that
also seems like overkill. Surely I'm missing something really simple.


Thanks!