Re: format short output with small numbers (bug #56936)

[John W. Eaton]

On 9/23/19 5:14 PM, Rik wrote:
> All,
>
> What should happen when we display small numbers with "format short"
> (default)?  Should we end up printing a lot of zeros?  That is what happens
> now.
>
> x = [-pi;0;pi];
> x*1e-6
> ans =
>
>    -0.0000031416
>                0
>     0.0000031416
>
> In earlier Octave versions we would switch over to scientific notation at a
> certain point.  These are the results from version 3.4.3
>
> octave-3.4.3:5> x*1e-3
> ans =
>
>    -0.0031416
>     0.0000000
>     0.0031416
>
> octave-3.4.3:6> x*1e-4
> ans =
>
>    -3.1416e-04
>     0.0000e+00
>     3.1416e-04

As I recall, Matlab uses a multiplier (Octave's fixed_point_format 
setting that is enabled when using --traditional).  But that doesn't 
account for the case you show above where it may show 0.00000 for small 
values instead of showing any digits.  For example, something like

  fixed_point_format (true);
  pi * [1e6; 1e-6]

I chose to switch automatically to avoid confusion because people might 
think that "0.00000" is exactly zero.  At that time, I don't remember 
Matlab displaying "0" to mean "exactly zero" (a feature that I like, 
BTW, thanks for making that change).

For those who want the display to be more like Matlab, is it sufficient 
to set fixed_point_format to true?  If so, then I'm not sure that there 
is anything we need to change, unless you are proposing that we enable 
fixed_point_format by default.

jwe