From: "Aleksi Niemelä" <aleksi.niemela@...>
Date: 2000-12-16T06:31:01+09:00
Subject: [ruby-talk:7350] Re: Different id's for the Object meta clas	s?

John Small also commented me privately, but I noticed some errors in my
assumptions, so I thought to correct at least them.

> Thanks for taking the time to respond.

No problem. These moments are opportunities -- to learn something new.

> I was under the impression that VALUE is just an unsigned long.  
> I was assuming this unsigned long is the pointer to the object 

Your impression and assumption was right, mine was wrong. ruby.h states 

  typedef unsigned long VALUE;
  typedef unsigned long ID;

> ..and the same thing as  Object#id returns.

But here it differs. Please look to object.c, which has code which converts
Ruby objects to IDs for basic types:

  rb_to_id(name)
      VALUE name;
  {
      ID id;

      switch (TYPE(name)) {
        case T_STRING:
          return rb_intern(RSTRING(name)->ptr);
        case T_FIXNUM:
          id = FIX2INT(name);
          if (!rb_id2name(id)) {
              rb_raise(rb_eArgError, "%d is not a symbol", id);
          }
          break;
        case T_SYMBOL:
          id = SYM2ID(name);
          break;
        default:
          rb_raise(rb_eTypeError, "%s is not a symbol", 
                   STR2CSTR(rb_inspect(name)));
      }
      return id;
  }

	- Aleksi