Implement missing type conversions for block diagram algebra #513

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1. murrayrm

   added this to the 0.9.x milestone on Jan 18, 2021
2. sawyerbfuller commented on Feb 11, 2021

   

   sawyerbfuller

   on Feb 11, 2021

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   (this was originally its own issue, #541, but I copied the comment into here and closed that issue to keep discussion about its possible implementation in this more general thread.)

   The following code causes a bug when it tries to raise an error:

   import control as ct
   import control.iosys as io
   2*io.ss2io(ct.ss(1,1,1,1))

   raise NotImplemented("Scalar multiplication not yet implemented")

   This is because InputOutputSystems define various methods, e.g. __mul__ that override those in StateSpace and some are not implemented yet.

   Options that come to mind if we want this to work better:

   1. Test for instances of StateSpace correctly and dispatch. This seems to be onerous and at odds with how inheritance ought to make things easier.
   2. In the __init__ method of LinearIOSystem, delete those methods
   3. move those operations to NonLinearIOSystem (and override as necessary in LinearIOSystem when it makes sense to create a new LinearICSystem)

   Related: many of the methods like __mul__ don't act on self and other but rather sys1 and sys2. This might still work, but I think the first argument should be self according to Python convention.
3. murrayrm commented on Dec 30, 2021

   

   murrayrm

   on Dec 30, 2021

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   A number of these conversions have been implemented in #672. Leaving this issue open since there are still a few cases that aren't handled (see table in tests/type_conversion_test.py).
4. murrayrm

   removed this from the 0.9.1 milestone on Dec 30, 2021