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 CALCULATOR EXAMPLE
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This model shows the use of the math library with the 
Behavior Annex and the Marzhin simulator.

A single thread runs periodically. 
It reads its inputs:
- two operands (data ports)
- one operation (event port)
and provides the corresponding result on an out data port

A simulation scenario generates automatically some inputs, 
and it is also possible to interact with the calculator 
thanks to the I/O interface box that can be opened by clicking
on the icon of the process (app) in the simulation display.