Re: [sqlite] using lemon

[Richard Hipp]

On Thu, May 10, 2012 at 4:59 PM, Baruch Burstein wrote:

> Can anyone suggest a lexical scanner generator that:
> a) Works well with Lemon?
> b) Is also thread-safe (like Lemon)?
>
> Does Flex work well with Lemon? (I think it is not thread-safe, but it is
> very popular and has plenty of examples around, which is also a plus for
> me)
>
> I am trying to learn a little about writing tokenizers/parsers, and thought
> a */Lemon combo would be better to learn if I don't have any previous
> experience anyway than Flex/Bison.
>

In my experience, lexical scanner generator programs like Flex are more
trouble than they are worth.  I find it far easier to write the lexer by
hand.  And you get a much smaller and faster lexer if you do it that way
too.

Example hand-written lexer code:
http://www.sqlite.org/src/artifact/1e86210d397?ln=107-378


>
> --
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> bigger and better idiot-proof programs, and the Universe trying to produce
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Re: [sqlite] using lemon

[Igmar Palsenberg]

> Can anyone suggest a lexical scanner generator that:
> a) Works well with Lemon?
> b) Is also thread-safe (like Lemon)?
> 
> Does Flex work well with Lemon? (I think it is not thread-safe, but it is
> very popular and has plenty of examples around, which is also a plus for me)
> 
> I am trying to learn a little about writing tokenizers/parsers, and thought
> a */Lemon combo would be better to learn if I don't have any previous
> experience anyway than Flex/Bison.

I've used re2c recently. It should meet your needs, and worked well in my case. 
There is a lack of documentation,
but I've pot most issues I've ran into on my blog : 
http://www.palsenberg.com/development/working-with-re2c-lessons-learned

If you live up to those rules, live should be pleasant :)



Igmar
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[sqlite] using lemon

[Baruch Burstein]

Can anyone suggest a lexical scanner generator that:
a) Works well with Lemon?
b) Is also thread-safe (like Lemon)?

Does Flex work well with Lemon? (I think it is not thread-safe, but it is
very popular and has plenty of examples around, which is also a plus for me)

I am trying to learn a little about writing tokenizers/parsers, and thought
a */Lemon combo would be better to learn if I don't have any previous
experience anyway than Flex/Bison.

-- 
Programming today is a race between software engineers striving to build
bigger and better idiot-proof programs, and the Universe trying to produce
bigger and better idiots. So far, the Universe is winning.  - Rich Cook
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Re: [sqlite] using lemon to create a c++ parser class

[Christian Smith]

Wilson, Ron uttered:

It has been a very long time since I have tinkered with lex/yacc but my 
current project requires a parser.  I'm thinking of learning lemon. 
Frankly, the sqlite code base is far more complex than what I will 
implement.  Is anyone willing to share a lemon parse.y code example for 
something less complex than SQL?



There are tutorials on the net that might be worth looking at, for 
example:

http://freshmeat.net/articles/view/1270/


  Also, i'm looking for advice on using 
lemon to make a c++ parser class instead of a global c parser function. 
Is it as simple as declaring the following?


%name MyParserClass::Parse

I'm pretty sure I can create the right c++ preamble with %include. 
Also, is there a cheap way to make lemon output a .cpp file besides 
renaming the output file?


Feel free to tell me I'm on a foolish quest if I am.



The C++ quest might be unnecassary, but I wouldn't say foolish. There is 
no problem linking C and C++ code. I'd say just leave the Parse function 
as a C function. You might even be able to make it static, thus limiting 
it's scope, and wrapping that static function in a class, but why bother?





RW



Christian


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[sqlite] using lemon to create a c++ parser class

[Wilson, Ron]

It has been a very long time since I have tinkered with lex/yacc but my current 
project requires a parser.  I'm thinking of learning lemon.  Frankly, the 
sqlite code base is far more complex than what I will implement.  Is anyone 
willing to share a lemon parse.y code example for something less complex than 
SQL?  Also, i'm looking for advice on using lemon to make a c++ parser class 
instead of a global c parser function.  Is it as simple as declaring the 
following?

%name MyParserClass::Parse

I'm pretty sure I can create the right c++ preamble with %include.  Also, is 
there a cheap way to make lemon output a .cpp file besides renaming the output 
file?

Feel free to tell me I'm on a foolish quest if I am.

RW


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