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From: "Nasser M. Abbasi" <nma@12000.org>
Newsgroups: comp.lang.ada
Subject: Re: Ada platforms and pricing, was: Re: a new language, designed
 for safety !
Date: Mon, 23 Jun 2014 20:18:00 -0500
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Date: 2014-06-23T20:18:00-05:00
List-Id: <comp.lang.ada>

On 6/23/2014 4:48 PM, Simon Wright wrote:
> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:
>
>> The idiom is: unless at gunpoint, never ever use FSM.
>
> There are times when state machines aren't appropriate and there are
> times when they are exactly the idiom you should be using.
>

I remember once struggling with so many IF/ELSEIF/ENDIF/WHILE, etc...
trying to implement something, and then I learned about FSM programming.

This was an application level, not low level system programming. Once
I setup things as FSM, things went smooth sailing.  Needed an
initial state, final state, setup a diagram that tells me the
event that causes which state to jump to which state. Once I drew
this diagram, the coding part was easy. One can even setup a
matrix that represent the algorithm.

For example, writing TCP/IP algorithm and other network
algorithms is nearly impossible without using the help of FSM.
Here are diagrams:

http://userpages.umbc.edu/~jeehye/cmsc491b/lectures/tcpstate/sld001.htm
http://en.wikipedia.org/wiki/Border_Gateway_Protocol
http://telescript.denayer.wenk.be/~hcr/cn/idoceo/tcp_linkstates.html

I think also for parsing text, setting up a FSM makes parsing things
much easier, and I used it for that also. FSM can be used for many other
things if one can identify all the states and all the events that
causes each state to switch to different state.

http://en.wikipedia.org/wiki/Finite-state_machine
  
--Nasser