Re: [jflex-users] merge more than one DFA into one

[Johnson W. <ins...@gm...>]

But, if so, how does the anti-virus work? They must find the virus and detect what kind of virus they are. Is it possible to modify the structure of NFA/DFA to make it have that function? 

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From: "Gerwin Klein" <ger...@ni...>
Sent: Monday, August 18, 2008 9:27 AM
To: "Johnson Wang" <ins...@gm...>
Cc: <jfl...@li...>
Subject: Re: [jflex-users] merge more than one DFA into one

> Johnson Wang wrote:
>> If I use JFlex to merge more than one DFA into one( use '|' connect each 
>> other), then about the final DFA, how to know which regular 
>> expression does the final states comes from? 
>> For instance:
>> Regular Expression1(r1):  a|b
>> Regular Expression2(r2):  a|c
>> We use '|' to connect these two regular expressions:  a|b|a|c
>> Then, about the final states, how do we know the states comes from r1 or r2?
> 
> There is no general way to know. If you want to distinguish two expressions, you 
> should match them separately in JFLex, otherwise the minimisation algorithm will 
> collapse the final states into one.
> 
> There is no speed penalty for matching them separately in JFlex (unless the two 
> DFAs have thousands of state).
> 
> Cheers,
> Gerwin
> 
> 
>