Re: GNU Emacs 21.2.1 (i386-debian-linux-gnu, X toolkit, Xaw3d scroll bars) of 2002-3-22 on raven, modified by Debian

[David Kastrup]

Mark Barnes <mbarnes@pacifier.com> writes:

> If I enter this expression in a buffer
> 
> (* 85 1.1)
> 
> and evaluate it it using Ctrl-x-e, I get the following answer
> displayed in the minibuffer:
> 
> 93.50000000000001
> 
> If I evaluate this expression
> 
> (- 93.5 (* 85 1.1))
> 
> I get this answer in the minibuffer:
> 
> -1.4210854715202004e-14
> 
> Is this documented in the reference manual?  I was unable to find
> anything about this kind of problem.

It is a facet of the well-known fact of life that 10*0.1 hardly ever
is 1.0.

In short: numerics.  0.1 has no exact representation in binary
floating point numbers.


-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum