From: Bryan Richardson <btricha@...>
Date: 2008-05-06T03:48:00+09:00
Subject: Re: Need more help with Ruby and C

------=_Part_20782_11749811.1210009460652
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Content-Disposition: inline

Jan,

Awesome... this now works perfectly!  Also, thanks for the heads-up on
having to return a value and using Qnil.  I was getting a segmentation fault
in irb that I wasn't sure about and it was because I wasn't returning
anything.

One side question... why is it called 'Qnil'?  What is the 'Q' for?

--
Thanks again!
Bryan

On Mon, May 5, 2008 at 10:38 AM, Jan Dvorak <jan.dvorak@kraxnet.cz> wrote:

> On Monday 05 May 2008 15:44:03 Bryan Richardson wrote:
> > Hi Jan,
> >
> > Alright, that makes sense, thanks for the information.  However, that
> > doesn't help me to understand how I can pass a Ruby array of objects to
> the
> > execute method.  Am I missing something here?  Can you help me with
> this?
> >
> The array is just an object (everything in ruby is object) which you can
> manipulate from C with rb_ary_* functions.  You wrote the code yourself:
>
>  VALUE foo = rb_ary_entry(foos, 0); // this will return the first element
> of
> the array
>
> now, rb_* functions operate on (and returns) ruby objects (VALUE), if you
> want
> to direclty use POD data types in C, you have to convert them, e.g. :
>
>  VALUE val = rb_iv_get(foo,"@value");
>  printf("Foo Value: %i\n", NUM2INT(val));
>
> or alternatively
>
>  printf("Foo Value: %i\n", NUM2INT(rb_iv_get(foo, "@value"));
>
> For integral types there are general macros INT2NUM (c to ruby) and
> NUM2INT
> (ruby to C), and their variants (FIX2INT,INT2FIX,..), for floats/doubles
> there is NUM2DBL (ruby to c) and rb_float_new() (C to ruby).
>
> Also, every method in ruby must return value, so if your function does not
> return anything, you have to explicitly return 'nil' with
>
>  return Qnil;
>
> Jan
>
>

------=_Part_20782_11749811.1210009460652--