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Finite state machine: Difference between revisions
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=={{header|Perl 6}}==
<lang perl6>#===== The state machine =====#
class StateMachine {
class State {...}
class Transition {...}
has State %!state;
has &.choose-transition is rw;
method add-state(Str $id, &action)
{
%!state{$id} = State.new(:$id, :&action);
}
multi method add-transition(Str $from, Str $to)
{
%!state{$from}.implicit-next = %!state{$to};
}
multi method add-transition(Str $from, $id, Str $to)
{
%!state{$from}.explicit-next.push: Transition.new(:$id, to => %!state{$to});
}
method run(Str $initial-state)
{
my $state = %!state{$initial-state};
loop {
$state.action.();
if $state.implicit-next -> $_ { $state = $_; }
elsif $state.explicit-next -> $_ { $state = &.choose-transition.(|$_).to; }
else { last; }
}
}
class Transition {
has $.id;
has State $.to;
}
class State {
has $.id;
has &.action;
has State $.implicit-next is rw;
has Transition @.explicit-next;
}
}
#===== Usage example: Console-based vending machine =====#
my StateMachine $machine .= new;
$machine.choose-transition = sub (*@transitions) {
say "[{.key + 1}] {.value.id}" for @transitions.pairs;
loop {
my $n = val get;
return @transitions[$n - 1] if $n ~~ Int && $n ~~ 1..@transitions;
say "Invalid input; try again.";
}
}
$machine.add-state("ready", { say "Please deposit coins."; });
$machine.add-state("waiting", { say "Please select a product."; });
$machine.add-state("dispense", { sleep 2; say "Please remove product from tray."; });
$machine.add-state("refunding", { sleep 1; say "Refunding money..."; });
$machine.add-state("exit", { say "Shutting down..."; });
$machine.add-transition("ready", "quit", "exit");
$machine.add-transition("ready", "deposit", "waiting");
$machine.add-transition("waiting", "select", "dispense");
$machine.add-transition("waiting", "refund", "refunding");
$machine.add-transition("dispense", "remove", "ready");
$machine.add-transition("refunding", "ready");
$machine.run("ready");</lang>
=={{header|Racket}}==
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