[Xitami-Dev] About Libero

[KERESZTFALVI Laszlo]

On Mon, Jan 21, 2002 at 01:31:37PM +0100, Pieter Hintjens wrote:
> It's a good idea, and indeed I generally prefer Flex to Libero for 
> designing parsers.  However... I once wrote a full COBOL lexical 
> analyser in Lex, hit several hard limitations and ended-up using a 

Basically, I suggest Bison which is a 'yacc' by GNU (AFAIK). So, it is a
compiler compiler. Flex is only a parser generator, no more!

Flex really supports states to enable very complicated context dependent
tokenization but this is usually not required and the syntax should be
realized in the Bison part.

Before I found Libero (and it was a love for the first sight) I had first
met the FSM design in real-life when one of my collegues who had worked on
cdrom controller hardwares ten years ago had used the FSM approach to
build data stream processor programs using a switch-case representation by
hand. So, I'd hunt for some tool to help the design-to-representation.
First, I'd wanted to use Bison and so grammars to build the FSM (bison
also generates state transition matrix in source format) but it had been
very very hard to construct a language from a flowchart. (I'd thought that
since the data stream can be processed it is a kind of protocol and
protocols are usually spoken :)

Even the FSM is a fine representation for both grammars and logic the
approach is very different I think. You mention that "Libero is not for
everything" in the doc. I think program logic usually use comparisions
(if/switch), iterations (loops) and exception handling while grammars use
substitution, recursion and pattern matching. We know that a recursion can
be transformed into iteration and so on, but I think a compiler can be
more efficient and extendable using grammar techniques while a program
logic can profit from flowchart-like clear transition description
technique.

I feel the difference is something like between C/C++/Java/whatever and
LISP/Scheme. While the previous is for programming logic the latter is for
pattern finding, decision trees, AI. Both can be used for other targets
but it'd be a pain! Just think about general, day-by-day coding in LISP!
OK, maybe thit was too hard, but feel the difference. That's why I think
Bison would be better for compiler issues like Libero and GSL. Libero will
still remain genious for logic!


Sorry being so long or talking about well-known issues.

Regards,
Laszlo

-- 
If carrots are so good for the eyes, how come I see so many dead rabbits
on the highway?