[erlang-questions] Erlang Numbers

[Richard A. O'Keefe]

On 18/06/2014, at 4:21 AM, Camille Troillard wrote:
> I understand Erlang uses the IEEE-754 specs for floating-point numbers arithmetic. So when I type in the console:
> 
> 1> 0.2 + 0.1.
> 0.30000000000000004
> 
> This is fine, I was expecting that. However, why the following works:
> 
> 2> 0.1.
> 0.1
> 
> Is it because of some rounding behaviour?

If the question you're asking is whether it is because
of some *Erlang-specific* rounding behaviour, the answer
is NO.

m% gsi
Gambit v4.6.0

> (+ 0.2 0.1)
.30000000000000004
> 0.1
.1
> (* 0.1 3)
.30000000000000004
> (- (* 0.1 10) 1)
0.
> (- (* (+ 0.1 0.2) 10) 3)
4.440892098500626e-16

What we want from output is
 - the shortest number that reads back as what we started with
and for 0.1 that happens to be "0.1".