Re: [jflex-users] Dynamic scanner generation

[Gerwin K. <ger...@ni...>]

Rob,

> I want to generate scanners dynamically (i.e. during the run of my
> program). My current approach is to let JFlex generate a scanner,
> compile the generated scanner and call it via exec(). IMHO, not a very
> elegant solution.

Not very elegant, but the easiest alternative currently, I suspect.


> I could find no help on how to use JFlex more dynamically, e.g.  use
> the generated DFA directly to parse the input, perhaps using a kind of
> closures for the action code.

I've had this idea in the back of my mind for quite some time now, but 
have never gotten around to giving it some serious thought. Most things 
that are static now could be easily replaced dynamically (DFA tables 
etc). The only problem I see is associating action code with the dynamic 
DFA. I've come up with the following alternatives so far:

* expect a generic interface for each action (i.e. call a method 
  void action(String,int) with the matched text and action number 
  or something like that)
  Pro: easy to do
  Con: not very flexible

* use reflection to specify method names for actions at run time
  Pro: flexible
  Con: high overhead, probably slow

Both alternatives require some hacking in the generator.

Cheers,
Gerwin