This example shows the handling of nested operation
calls. It is based on the factorial function
with return type Integer.
The operation can be used as query operation and
with openter and opexit, too.

NestedOperationCalls.use:
one Class Rec
one operation fac, computing and returning the factorial
of the functions argument
this operation is defined as query and has
pre- and postconditions


NestedOperationCalls.cmd:
calls the Function three times with different
arguments (not as query)
and it ends the calls in the same order
all pre- and postconditions evaluate to true
