Re: [boost] [fsm review] Comparison with ad-hoc FSM coding

From: Phil Endecott (spam_from_boost_dev_at_[hidden])
Date: 2008-08-17 18:25:05

Andrey Semashev wrote:
> Phil Endecott wrote:
>> Andrey Semashev wrote:
>> 
>>> IMO, undefined behavior usually is a design flaw, and this case is
>>> clearly one of the "usual" ones. Otherwise, like I said, you don't need
>>> FSM, because its whole purpose is to _define_ the behavior.
>> 
>> I disagree.  If I have a guarantee of how the environment will behave it
>> is unnecessary to check it, except perhaps in some sort of debug mode. 
>
> Agreed. But in such a case, do you need an FSM in the first place? If
> you have the guarantee that function A will always be called before
> function B, you will simply rely on it and assume that while in B, A has
> already been called.

An environment that makes guarantees about how it will or will not 
behave is not generally a completely deterministic environment.

Example: say I'm receiving UTF-8, and I'm guaranteed by the sender that 
it's valid UTF-8.  I still need to track the state of the stream as I 
process the bytes, even though I'm going to allow undefined behaviour 
(either in the C++ language sense, or in some other sense) if those 
bytes are invalid.  This particular problem could certainly be usefully 
expressed using an FSM.

But don't worry if you disagree; this is unimportant.  The intention of 
my original message was to suggest that your library seems to add a lot 
of verbosity to my implementation, without much obvious benefit.  I 
would like to be convinced otherwise, preferably through examples.

Phil.