Finite state machine: Difference between revisions

</pre>

=={{header|Ol}}==

<lang scheme>

(import (scheme read))

; finite state machine

(define (state-machine states initial-state)

(let loop ((state initial-state))

(let*((action ((states state) 'enter #f))

(process-enter (if (function? action) (action)))

(next-state (if (symbol? action) action

else

((states state) (string->symbol (symbol->string (read))) state))))

(loop next-state))))

; task states

(define states {

'ready {

'enter (lambda () (print "Write (d)eposit for deposit and (q)uit to exit."))

'd 'waiting

'deposit 'waiting

'q 'exit

'quit 'exit

}

'exit {

'enter (lambda () (halt 1))

}

'waiting {

'enter (lambda () (print "Write (s)elect for dispense or (r)efund for refund."))

's 'dispense

'select 'dispense

'r 'refunding

'refund 'refunding

}

'dispense {

'enter (lambda () (print "Write (r)emove to finish action."))

'r 'ready

'remove 'ready

}

'refunding {

'enter 'ready

}

})

; run

(state-machine states 'ready)

</lang>

{{Out}}

<pre>

Write (d)eposit for deposit and (q)uit to exit.

d

Write (s)elect for dispense or (r)efund for refund.

f

Write (s)elect for dispense or (r)efund for refund.

f

Write (s)elect for dispense or (r)efund for refund.

s

Write (r)emove to finish action.

r

Write (d)eposit for deposit and (q)uit to exit.

d

Write (s)elect for dispense or (r)efund for refund.

s

Write (r)emove to finish action.

r

Write (d)eposit for deposit and (q)uit to exit.

q