From: Bryan Richardson <btricha@...>
Date: 2008-05-06T02:44:58+09:00
Subject: Re: Help with rb_iv_set

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Perfect... :).  Thanks Tim!

On Mon, May 5, 2008 at 10:34 AM, Tim Pease <tim.pease@gmail.com> wrote:

>
> On May 5, 2008, at 7:35 AM, Bryan Richardson wrote:
>
>  Hi Rick,
> >
> > So you're saying that by doing it the way I was doing it (using
> > rb_float_new) I am indeed doing it correctly?
> >
> >
> To be explicit about your specific case ...
>
> rb_iv_set(self, "@voltage", rb_float_new(1.01));
>
>
> Blessings,
> TwP
>
>
>
>  --
> > Thanks!
> > Bryan
> >
> > On Sun, May 4, 2008 at 9:29 PM, Rick DeNatale <rick.denatale@gmail.com>
> > wrote:
> >
> >  On Sun, May 4, 2008 at 11:13 PM, Bryan Richardson
> > > <btrichardson@gmail.com> wrote:
> > >
> > > > Hello all,
> > > >
> > > > I'm trying to use rb_iv_set to set a double value in a C extension
> > > > I'm
> > > > writing.
> > > >
> > > > rb_iv_set(self, "@voltage", 1.01);
> > > >
> > > > This doesn't seem to work, as I get a '0' instead of '1.01'.  If I
> > > > use
> > > > rb_float_new(1.01), then it works.  However, the voltage value in my
> > > > C
> > > > structure is a double, and rb_double_new doesn't exist.
> > > >
> > > > Any suggestions?
> > > >
> > >
> > > rb_iv_set needs a VALUE for the third parameter.
> > > and the value of a Ruby float is a C double:
> > >
> > > From the 1.8.6 source:
> > >
> > > in ruby.h
> > >
> > > VALUE rb_iv_set _((VALUE, const char*, VALUE));
> > >
> > > and also:
> > >
> > > struct RFloat {
> > >  struct RBasic basic;
> > >  double value;
> > > };
> > >
> > > And from numeric.c
> > >
> > > VALUE
> > > rb_float_new(d)
> > >  double d;
> > > {
> > >  NEWOBJ(flt, struct RFloat);
> > >  OBJSETUP(flt, rb_cFloat, T_FLOAT);
> > >
> > >  flt->value = d;
> > >  return (VALUE)flt;
> > > }
> > >
> > >
> > > --
> > > Rick DeNatale
> > >
> > > My blog on Ruby
> > > http://talklikeaduck.denhaven2.com/
> > >
> > >
> > >
>
>

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