MATLAB: How to implement a zero-sized or empty signal in Simulink

simulink

I want to achieve the following functionality in Simulink:
>> a = [1 2]; % Non-empty array
>> b = []; % Empty array
>> c = [a;b]; % Successful concatenation
To achieve this, I need a way to represent a zero-sized signal or empty array. How can I do this today?
Workaround (from R2010b) is given here:
https://www.mathworks.com/matlabcentral/answers/94958-how-can-i-implement-a-zero-sized-signal-using-blocks-in-simulink-7-6-r2010b
However, I want to know if there is an official way to represent a zero-sized signal or empty array.

Best Answer

It is certainly possible to have a 'zero-sized' or "empty" signal in Simulink. The documentation on Variable-Size Signal Basics:
https://www.mathworks.com/help/releases/R2020b/simulink/ug/variable-size-signal-basics.html#br932gn
gives specifications on when empty signals may not be used, i.e. in blocks which modify signal dimensions. 
The attached sample models demonstrate the implementation of such signals. 
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