From: Daniel Berger <Daniel.Berger@...>
Date: 2005-11-04T02:02:35+09:00
Subject: Re: Question about NUM2LONG, symbols

ts wrote:
>>>>>>"D" == Daniel Berger <Daniel.Berger@qwest.com> writes:
> 
> 
> D> Foo.new.test("foo".to_sym) # NUM: 10201 - yikes!
> 
> moulon% cat aa.c
> #include "ruby.h"
> #include <stdio.h>
> 
> static VALUE
> aa_to_int(VALUE self)
> {
>     return INT2FIX(12);
> }
> 
> static VALUE 
> aa_test(VALUE self)
> {
>     printf("NUM: %ld\n", NUM2LONG(self));
> 
>    return Qnil;
> }
> 
> void Init_aa(){
>    VALUE cAa = rb_define_class("Aa", rb_cObject);
>    rb_define_method(cAa, "test", aa_test, 0);
>    rb_define_method(cAa, "to_int", aa_to_int, 0);
> }
> 
> moulon% 
> 
> moulon% ruby -raa -e 'Aa.new.test'
> NUM: 12
> moulon% 
> 
> 
> Guy Decoux

Ok, thanks Guy, I get it - internally it calls rb_num2long(), which in turn 
tries to call a to_int method.  Since the Symbol class defines to_int, I get 
that result.

I guess it would be nice if we had a macro that raised a TypeError on anything 
except a Fixnum, Float or Bignum.  Otherwise, aren't all C extension writers 
relegated to doing explicit checks against Symbols (the way rb_ary_ref() does 
in array.c) if we really want to make our code bulletproof?  That, or lots of 
Check_Type() functions sprinkled throughout our code?

I suppose I just want a version of rb_num2long() that changes the default in 
the switch statement to something like this:

default:
    rb_raise(rb_eTypeError, "not a Fixnum, Float or Bignum");

Thanks,

Dan