Hi, I have been playing around with the boost MSM libraries, to know more about them. I am creating a vending machine simulation with a sub-machine for accepting payment from the user. The vending machine has 3 states: waiting (where the machine just waits for the user to start processing), selection (where user selects a product. The machine makes a transition to this state from "waiting" state if the event "key_press" occurs and if the key pressed is the start button (checked by a guard condition).). After a product is selected the machine goes in payment state, which is a submachine that accepts payment in quarters. After the payment is received (it is fixed $1 for all products, just to make it simple) the machine again goes in the waiting state dispensing the product (action: dispatch_item). The submachine Payment has 4 states: Payment_init which just displays a message and then makes an immediate automatic transition to the next state "Paying". In this state the machine just waits for the "coin_insert" event to occur (which represents inserting a quarter). Once the "coin_insert" event occurs it makes a transition to "check_payment" state which checks if sufficient amount was paid. If not it again makes an automatic transition to "Paying" state, else it moves to the "Payment_done" state which is the last state in the submachine. This state generates an event "last_state" which is an indicator that the payment has been made and should cause a transition from the submachine "Payment" to waiting state (which I am not observing). The transition tables for both the machines are: (btw I am using the functors as the front end.) Table for vending machine: // +---------------------+-----------------------+----------------------+---------------------+------- Row < waiting, key_press, selection, none, is_start>, /// If start button pressed, go to selection state Row < waiting, key_press, waiting, none, is_cancel>, // If cancel pressed stay in the waiting state Row < selection, key_press, Payment, none, is_number>, //If a product number pressed go to payment Row < selection, key_press, waiting, none, is_cancel>, // If cancel pressed go to Row < Payment, key_press, waiting, none, is_cancel>, Row < Payment, last_state, waiting, dispatch_item, none> //the last_state event is generated in the // "payment_done" state of the Payment submachine // +---------+-------------+---------+---------------------+----------------------+ Table for Payment machine: // +---------------------+-----------------------+----------------------+---------------------+------- Row < Payment_init, none, Paying, none, none >, // Just make an auto transition after displaying a msg Row < Paying, coin_insert, check_payment, none, none>, Row < check_payment, none, Paying, none, is_not_paid>, //If enough money received Row < check_payment, none, payment_done, none, is_paid> // +---------+-------------+---------+---------------------+----------------------+ The code for payment_done state is: struct payment_done: public msm::front::state { template<class Event, class FSM> void on_entry(Event const &, FSM &fsm) { cout << "---------------" << endl; cout << "Payment_done" << endl; fsm.process_event(last_state()); } }; The events that I gave as an input to the state machine are: Event inputs: //vm = vending machine vm->start(); vm->process_event(key_press(START)); //press start vm->process_event(key_press('5')); // select a product vm->process_event(coin_insert(0.25)); // Make payment in quarters and "50 cents"! vm->process_event(coin_insert(0.25)); vm->process_event(coin_insert(0.5)); I am printing out the event/state/action/guard condition name on entry. Here is the output: Output: Trying out the Boost Meta State Machine --------------- waiting Please press start button --------------- Event key_press Entered key: s // s = start --------------- Guard condition is_cancel --------------- Guard condition is_start --------------- selection Select a product: --------------- Event key_press Entered key: 5 --------------- Guard condition is_cancel --------------- Guard condition is_number entering: Payment // submachine --------------- Payment_Init --------------- Paying template Insert coins: //msg displayed in the state //plz ignore the word "template" in the line --------------- Event coin_insert Inserted $0.25 --------------- check_payment Checking if full payment made in check_payment. --------------- Guard condition is_paid //check if full payment received --------------- Guard condition is_not_paid //check if full payment not received (in which case move to Paying state) --------------- Paying template Insert coins: //msg displayed in the state //plz ignore the word "template" in the line --------------- Event coin_insert Inserted $0.25 --------------- check_payment Checking if full payment made in check_payment. --------------- Guard condition is_paid //check if full payment received --------------- Guard condition is_not_paid //check if full payment not received (in which case move to Paying state) --------------- Paying template Insert coins: //msg displayed in the state //plz ignore the word "template" in the line --------------- Event coin_insert Inserted $0.5 --------------- check_payment Checking if full payment made in check_payment. --------------- Guard condition is_paid //check if full payment received (which is, in this case. so move the payment_done state) --------------- Payment_done --------------- Event last state //The event occurs but the transition does not As you can see the event "last_state" is occurring in the payment_done state but the transition is not taking place. I can post the entire code is someone is interested but I am just playing around with the libraries so the code (and some logic too) is not sophisticated at all. Still I can post it if someone wants to take a look at it. Thanks! -- View this message in context: http://boost.2283326.n4.nabble.com/Boost-MSM-Can-not-get-out-of-the-submachi... Sent from the Boost - Users mailing list archive at Nabble.com.