From: Dennis Schridde <devurandom@...>
Date: 2005-09-09T20:38:02+09:00
Subject: Re: Embedding Ruby into C

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Am Freitag, 9. September 2005 10:26 schrieb BearItAll:
> On Thu, 08 Sep 2005 02:13:31 +0900, Dennis Schridde wrote:
> > Am Mittwoch, 7. September 2005 16:04 schrieb Dennis Schridde:
> >> Hi!
> >> I am a Ruby newb(using it since a few days and read the book just a few
> >> weeks ago) and would like to embed Ruby into a C program.
> >>
> >> I read the chapter about it in the PickAxe and this Wiki article:
> >> http://www.rubygarden.org/ruby?EmbedRuby
> >>
> >> The problem is that the PickAxe does some fancy this (it can't be that
> >> complicated, can it?) and the Wiki doesn't say anything definitive at
> >> all.
> >>
> >> I'd like to get an example, that is as easy as possible, will definete=
ly
> >> work with Ruby 1.8 and could be called a "good way".
> >> It should define a C function, load a Ruby script which defines a Ruby
> >> function, call the Ruby function from C and call the C function from
> >> Ruby. It should explain different return/parameter types and multiple
> >> parameters. The C program should report if the Ruby script had a bug in
> >> it.
> >>
> >> All in complete Ruby/C files, please.
> >>
> >> Thanks in advance,
> >> Dennis
> >
> > P.S. I forgot to mention that this should/will replace the above
> > mentioned Wiki.
> > So the best would be if the base example would be pretty simple and more
> > features were added to it in additional examples.

Thanks very much for you effort!

> The example below is from sourceforge, but before we get that far I'll
> make the the point that I believe embedding Ruby into C/C++ is the wrong
> way round.
> I would say that using your C/C++ libs inside Ruby is the right way round.
Well, I wanted to see if I could extend my application with scripting suppo=
rt,=20
so this is the way to go.

> But also, although I am including the sourceforge example because it
> directly answers the question you asked, I would say that the example they
> show is based on giving a traditional 'embedded' approach. But for the
> particular example they give they have Ruby dealing with data then the C++
> controlling the view.
But I think this is again very complex and it uses C++, what seems to make =
it=20
relatively different from a plain C approach.
The use a baseclass for both their Ruby and C++ classes. That is simply not=
=20
possible in my app.
It uses exceptions for error handling, what is not possible with C, as far =
as=20
I know.

And it is not suited for the wiki I mentioned.

> That is a classic modular split that all software should take of cause,
> but it begs the question, 'For two different languages, if the functions
> of the two are so separate then why embed rather than simply communicate
> between two modules'. I agree that there are arguments for and against,
> just want to point out that the traditional embedded approach on modern
> fast machines is not always necessary or the best way to solve
> these problems.
>
> Anyway the link that tells you how to do it all is,
>
> http://metaeditor.sourceforge.net/embed

Pseudocode of what I imagined:

C-File:
int c_function( float param1, const char * param2);
float c_global =3D 0.5f;

int main(void)
{
	ruby_function( p1, p2);
}

Ruby-File:
def ruby_function( param1, param2 )
	print( c_function( c_global, param2 ) )
end


Perhaps as extension to that:

C-File:
void c_callback_to_ruby( XXX ruby_function_cb )
{
	ruby_function_cb( p1, p2 );
}

Ruby-File:
def ruby_function2
	c_callback_to_ruby( ruby_function ) # ruby_function -> see above
end

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