From: Ryan Davis <ryand-ruby@...>
Date: 2006-04-15T03:02:55+09:00
Subject: Re: Calling instance_eval on a block in C


On Apr 14, 2006, at 10:33 AM, John Lam wrote:

> If I have this ruby method:
>
> def eval_it(obj, &b)
>   obj.instance_eval(&b)
> end
>
> How do write the C code to make this happen? If I do this:
>
> rb_funcall(obj, rb_intern("instance_eval"), 1, zz);
>
> Ruby is apparently expecting a String for the type of zz.

Hey John,

I'm not positive, but I don't think it is possible, because of the  
block. Blocks come in through manipulated ruby_frames, even if they  
look like they are passed in via shells. Clues being:

static VALUE
rb_f_block_given_p()
{
     if (ruby_frame->prev && ruby_frame->prev->iter == ITER_CUR &&  
ruby_block)
         return Qtrue;
     return Qfalse;
}

and the first hunk of specific_eval reading:

     if (rb_block_given_p()) {
         if (argc > 0) {
             rb_raise(rb_eArgError, "wrong number of arguments (%d  
for 0)", argc\
);
         }
         return yield_under(klass, self);
     }