This model demonstrates the interoperability of CAL functions and Ptolemy functions.
The Fac actor creates a simple CAL function, which is applied in the Apply
expression actor.
Conversely, the ApplyF CAL actor takes a Ptolemy expression language function
as argument and uses it inside the CAL code as if it was a CAL function.
In fact, CAL functions are represented as Ptolemy FunctionTokens, and as a consequence
virtually indistinguishable from functions generated by the Ptolemy expression language.
This means that all the CAL facilities become immediately available in Ptolemy, such
as recursion and mutually recursive functions.