I will assume some simple linear systems knowledge but the question can be generalized to any operator that implements __mul__ and __rmul__ methods.
Motivation: I am trying to implement a gain matrix, say 3x3 identity matrix, for time being with a single input single output (SISO) system that I have implemented as a class modeling a Transfer or a state space representation. In the typical usecase, suppose you would like to create an n-many parallel connections with the same LTI system sitting at each branch. MATLAB implements this as an elementwise multiplication and returning a multi input multi output(MIMO) system. G = tf(1,[1,1]); eye(3)*G produces (manually compactified) ans = From input 1 to output... [ 1 ] [ ------ , 0 , 0 ] [ s + 1 ] [ 1 ] [ 0 , ------ , 0 ] [ s + 1 ] [ 1 ] [ 0 , 0 , ------ ] [ s + 1 ] Notice that the result type is of LTI system but, in our context, not a NumPy array with "object" dtype. In order to achieve a similar behavior, I would like to let the __rmul__ of G take care of the multiplication. In fact, when I do G.__rmul__(np.eye(3)) I can control what the behavior should be and I receive the exception/result I've put in. However the array never looks for this method and carries out the default array __mul__ behavior. The situation is similar if we go about it as left multiplication G*eye(3) has no problems since this uses directly the __mul__ of G. Therefore we get a different result depending on the direction of multiplication. Is there anything I can do about this without forcing users subclassing or just letting them know about this particular quirk in the documentation? What I have in mind is to force the users to create static LTI objects and then multiply and reject this possibility. But then I still need to stop NumPy returning "object" dtyped array to be able to let the user know about this. Relevant links just in case the library : https://github.com/ilayn/harold/ the issue discussion (monologue actually) : https://github.com/ilayn/harold/issues/7 The question I've asked on SO (but with a rather offtopic answer): https://stackoverflow.com/q/40694380/4950339 ilhan
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