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From: "Mattmann, Chris A (388J)" <chris.a.mattmann@jpl.nasa.gov>
To: "lucy-dev@incubator.apache.org" <lucy-dev@incubator.apache.org>
Date: Mon, 21 Feb 2011 12:29:00 -0800
Thread-Topic: [lucy-dev] Porting Clownfish compiler to C
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Subject: Re: [lucy-dev] Porting Clownfish compiler to C

Hey Marvin,

Is there any reason to look at SWIG for the language bindings (not now, but=
 maybe later?). I know SWIG is pretty good at taking C code and generating =
language specific bindings and that SVN uses it.

Cheers,
Chris

On Feb 21, 2011, at 12:16 PM, Marvin Humphrey wrote:

> Greets,
>=20
> The porting of the Clownfish compiler to C has been underway for the last
> several weeks.  As previously discussed, this move was necessary in order=
 to
> replace the Perl-licensed CPAN module Parse::RecDescent with the public-d=
omain
> Lemon parser generator, written in C by SQLite author Richard Hipp. =20
>=20
> Now that LEGAL-86 has finally been resolved favorably, usage of
> Parse::RecDescent no longer blocks our 0.1.0-incubating release, taking s=
ome
> of the urgency out of the task.  Nevertheless, trunk/clownfish is in a
> transitional state right now and I think it makes sense to push through t=
o a
> coherent stopping point.
>=20
> The end goal is to have Clownfish entirely in C, as once that is done, it
> eliminates the dependency for other Lucy host language bindings on Perl.
> These are the stages of the transition:
>=20
>  1. *DONE* Migrate to an inside-out object model within the Clownfish
>     compiler internals.  This makes it easier to move piecemeal from Perl
>     implementations to XS to C implementations.
>  2. *DONE* Eliminate sophisticated usage of polymorphism by Clownfish
>     compiler components, e.g. by rolling up many Type classes into one
>     module.  In our C-based compiler, we can still use crude inheritance
>     based on struct layout and casting, but we don't want to require meth=
od
>     overriding if we can help it.
>  3. *UNDERWAY* Port primary Clownfish components to thin XS wrappers arou=
nd C
>     implementations.  This includes everything within trunk/clownfish/lib=
/
>     except the items under lib/Clownfish/Binding/ and lib/Clownfish/Parse=
r.pm.
>  4. Port everything under trunk/clownfish/lib/Clownfish/Binding/ to XS
>     wrappers around C code.
>  5. Port Clownfish/Parser.pm to an XS wrapper around a C implementation u=
sing
>     Lemon.
>  6. Port all the test files in trunk/clownfish/t/ to C, using the test
>     harness code provided by Charmonizer.
>  7. Change the interface by which bindings are spec'd to e.g. parse stati=
c
>     JSON files rather than be invoked from Perl code, and change over all=
 the
>     binding specs embedded within .pm files in trunk/perl/lib/ to use the=
 new
>     interface.
>  8. Remove all Perl/XS from trunk/clownfish/.
>=20
> In order to eliminate Parse::RecDescent as a dependency, we need to get
> through stage 5, and that had been my previous goal for the 0.1.0-incubat=
ing
> release.  Now it seems to make sense to pause after either stage 3 or sta=
ge 4.
>=20
> I look forward to completing all 8 stages, as once all the Perl code is
> eliminated, it will make it easier for a larger Lucy community whose prim=
ary
> expertise is in C to grok, to maintain and to write new host language
> bindings.
>=20
> Marvin Humphrey
>=20


++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Chris Mattmann, Ph.D.
Senior Computer Scientist
NASA Jet Propulsion Laboratory Pasadena, CA 91109 USA
Office: 171-266B, Mailstop: 171-246
Email: chris.a.mattmann@nasa.gov
WWW:   http://sunset.usc.edu/~mattmann/
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Adjunct Assistant Professor, Computer Science Department
University of Southern California, Los Angeles, CA 90089 USA
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++