From: Chad Perrin <perrin@...>
Date: 2007-03-09T08:04:54+09:00
Subject: Re: Paul Graham explains Ruby symbols

On Fri, Mar 09, 2007 at 06:11:43AM +0900, Rick DeNatale wrote:
> On 3/8/07, Chad Perrin <perrin@apotheon.com> wrote:
> >On Thu, Mar 08, 2007 at 02:17:13AM +0900, Rick DeNatale wrote:
> >> On 3/6/07, Luciano Ramalho <ramalho@gmail.com> wrote:
> >> >Paul Graham offers this excellent explanation for the symbol type:
> >> >
> >> >"Symbols are effectively pointers to strings stored in a hash table.
> >> >So you can test equality by comparing a pointer, instead of comparing
> >> >each character." [1]
> >> >
> >> >Of course, he's talking about symbols in Lisp, but what he says
> >> >applies equally well to Ruby and Smalltalk.
> >>
> >> I find this a little too implementation-centric a description.
> >
> >Unfortunately, there's no way to differentiate a string literal from a
> >symbol in a definitive manner without brushing up against
> >implementation.  At least, I haven't seen such a thing yet.
> 
> lets see
> 
> def is_symbol?(arg)
>   arg.object_id == arg.to_sym.object_id rescue false
> end

. . . which brushes up against implementation.

-- 
CCD CopyWrite Chad Perrin [ http://ccd.apotheon.org ]
"The first rule of magic is simple. Don't waste your time waving your
hands and hopping when a rock or a club will do." - McCloctnick the Lucid