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/*!

    \example statemachine/factorial

    \title Factorial States Example

    The Factorial States example shows how to use \l{The State Machine

    Framework} to calculate the factorial of an integer.

    The statechart for calculating the factorial looks as follows:

    \img factorial-example.png

    \omit

    \caption This is a caption

    \endomit

    In other words, the state machine calculates the factorial of 6 and prints

    the result.

    \snippet examples/statemachine/factorial/main.cpp 0

    The Factorial class is used to hold the data of the computation, \c x and

    \c fac. It also provides a signal that's emitted whenever the value of \c

    x changes.

    \snippet examples/statemachine/factorial/main.cpp 1

    The FactorialLoopTransition class implements the guard (\c x > 1) and

    calculations (\c fac = \c x * \c fac; \c x = \c x - 1) of the factorial

    loop.

    \snippet examples/statemachine/factorial/main.cpp 2

    The FactorialDoneTransition class implements the guard (\c x <= 1) that

    terminates the factorial computation. It also prints the final result to

    standard output.

    \snippet examples/statemachine/factorial/main.cpp 3

    The application's main() function first creates the application object, a

    Factorial object and a state machine.

    \snippet examples/statemachine/factorial/main.cpp 4

    The \c compute state is created, and the initial values of \c x and \c fac

    are defined. A FactorialLoopTransition object is created and added to the

    state.

    \snippet examples/statemachine/factorial/main.cpp 5

    A final state, \c done, is created, and a FactorialDoneTransition object

    is created with \c done as its target state. The transition is then added

    to the \c compute state.

    \snippet examples/statemachine/factorial/main.cpp 6

    The machine's initial state is set to be the \c compute state. We connect

    the QStateMachine::finished() signal to the QCoreApplication::quit() slot,

    so the application will quit when the state machine's work is

    done. Finally, the state machine is started, and the application's event

    loop is entered.

 */