[ragel-users] State chart style and entering actions

Shawn Hoover shawn at bighugh.com
Wed Jul 27 15:00:05 UTC 2011


I'm using the state chart style for processing application logic. So far
I've gotten by with finishing actions attached to specific events, but now
I'd like to use an entering action for an entire labeled expression. Here's
an example:

machine := (
start: START -> A,
A: (IDLE -> A |
   POLL @poll OPEN -> A |
   POLL @poll CLOSED -> B), >~a_entry,
B: (IDLE -> B |
   EXIT -> final)

I would like to execute a_entry once and only once when the A "loop" is
entered. It does execute on entrance, but then it also executes every time I

Is there a way to make a_entry execute only once while still using state
charts and the union operator in the same structure? I suppose the following
would work:

A: (IDLE | POLL @poll OPEN)* POLL @poll CLOSED -> B >~a_entry;

But I'd like to retain the original structure if there's a better way to
attach the action.

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