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Re: Using empty_string as the only "" string


From: Juanma Barranquero
Subject: Re: Using empty_string as the only "" string
Date: Wed, 25 Apr 2007 00:59:56 +0200

On 4/25/07, Miles Bader <address@hidden> wrote:

You are misunderstanding what guarantees are made in lisp about object
identity.

I don't think there's such thing as "lisp", but certainly I'm not
misunderstanding what guarantees are made about Emacs Lisp. I'm
talking about the "guarantee" implicit in its current behaviour. For
the umpteen time, I *know* (eq "" "") => t is not forbidden; just
unexpected.

thus you
get something like (eq 0.0 0.0) => t, but (eq 1987.57 1987.57) => nil.

That's the reason I talked about 1.0, not 1987.57. 1.0 is a small and
commonly used number. An implementation canonicalizing 0.0 could
reasonably be expected to do the same for several other "interesting"
real numbers.

[There's also the traditional fixnum/bignum divide, which has a similar
effect on integers.]

And that's the reason I used reals and not integers in my example.

Could we please stop Lisp 101?

            Juanma




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