Re: Q: what parser generator can do this?

Martin Gijsen said:


> So can anyone out there
> recommend a parser generator that can do all of the following:
>
> - multiple entry points (multiple parsers, shared code)
> - supports parameters to rules and local variables (like LLgen)
> - error mechanism that enables context specific error messages
> (such as: "bar" expected after "foo")
> - generates C or C++ code (Unix environment)


PAISLEI seems to meet all the above requirements.


It can generate multiple grammars that are re-entrant. (You could
call a PAISLEI grammar for language B from the production code of
parser A, to parse a sub-language, or <SCRIPT> section in HTML, for
instance.)


You can also extract substrings into "casts" that are easily
accessible from production code, using a macro, so that:


        ['('$
                [^
                        [*?
                ['variable'^
        [')'$


Would match (foobar), and in your C++ code, you can reference the
lexeme "foobar" like this:


        __PSL_CAST("variable")


This is not quite "variables and parameters..." but it works.


You can generate specific error messages, like this:


        ['('$
                ['a';'b';c' / "A, B, or C expected!" / $
        [')'$


The above would generate the message "A, B, or C expected!" if it
encountered (d), for instance.


Finally, PAISLEI patterns can be written as traditional regular
expressions if you are more comfortable with those, like this:


        <RE([a-zA-Z_][a-zA-Z0-9_]+)>


Although PAISLEI itself runs only on Win32 systems, the classes it
generates have proven to be portable to the *nix C++ compilers. You
can test and generate your grammar on a Win32 system, compile it on a
*nix system.


Version 2.0 is currently in beta at http://www.qtj.net/~lpm/beta/


(If that link doesn't work due to DNS problems, try:
http://24.113.4.170/~lpm/beta )


Cheers,
--
Quinn Tyler Jackson
http://www.qtj.net/~quinn/

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