language_emptiness [-h] [-v] [-a]
Checks for the language emptiness.
If -a is given the check is performed by verifying whether
all initial states are included in the set of fair states. If it is
the case from all initial states there exists a fair path and thus
the language is not empty. On the other hand, if no -a is
specified, the check is performed by verifying whether there exists
at least one inital state that is also a fair state. In this case
there is an initial state from which it starts a fair path and thus
the lnaguage is not empty.
if -v is specified, then some information on the set of
initial states is printed out too.