Re: (- 2.8 1.6) ; 1.1999999999999997

[Joost Kremers]

On Mon, Feb 10 2020, Emanuel Berg via Users list for the GNU Emacs 
text editor wrote:
> What's this?
>
>     (- 2.8 1.6) ; 1.1999999999999997
>
> With the TI-84 Plus,
>
>     2.8-1.6=1.2
>
> Normally I'm all pro-Lisp but here...
>
> Actually zsh also reports
>
>     echo $(( 2.8 - 1.6 )) # 1.1999999999999997

joost@Swift:~$ clojure
Clojure 1.9.0
user=> (- 2.8 1.6)
1.1999999999999997
user=> (+ 0.1 0.2)
0.30000000000000004
user=> <C-d>
joost@Swift:~$ python
Python 2.7.17 (default, Nov  7 2019, 10:07:09)
[GCC 7.4.0] on linux2
Type "help", "copyright", "credits" or "license" for more 
information.
> > > 2.8 - 1.6
1.1999999999999997
> > > 0.1 + 0.2
0.30000000000000004
> > > <C-d>
joost@Swift:~$ 

> so perhaps some CPU (ALU) thing?

It's a binary thing, and it's well-known:

https://floating-point-gui.de/

--
Joost Kremers
Life has its moments