[Scilab-users] display of complex/not real numbers, again

[Stéphane Mottelet]

Le 13/09/2019 à 16:52, Samuel Gougeon a écrit :
> Le 13/09/2019 à 14:22, Stéphane Mottelet a écrit :
>>
>> However, as I already said it elsewhere, some glitches such as the 
>> following  one do occur (see the display of whole x)
>>
>> --> x=1:0.1:2
>>  x  =
>>    1.   1.1   1.2   1.3   1.4   1.5   1.6   1.7000000   1.8 1.9   2.
>>
>
> I agree with Christophe. This output is OK for me. Aestheticism must 
> be encouraged provided that it does not truncate or downgrade the 
> information.
>
> About padding every number: Not OK. This would kill one of the assets 
> of the "v" format: its compacity.
>
> About the fact that 1.7 can't be exactly encoded: It is very 
> surprising for a so limited decimal number. But OK. I am also quite 
> surprised that, in this series, only 1.7 can't be exactly encoded.
>
bitstring allows to see that only 1, 1.5 and 2 are exactly encoded

--> bitstring(1:0.1:2)'
  ans  =

!0011111111110000000000000000000000000000000000000000000000000000 !
! !
!0011111111110001100110011001100110011001100110011001100110011010 !
! !
!0011111111110011001100110011001100110011001100110011001100110011 !
! !
!0011111111110100110011001100110011001100110011001100110011001101 !
! !
!0011111111110110011001100110011001100110011001100110011001100110 !
! !
!0011111111111000000000000000000000000000000000000000000000000000 !
! !
!0011111111111001100110011001100110011001100110011001100110011010 !
! !
!0011111111111011001100110011001100110011001100110011001100110100 !
! !
!0011111111111100110011001100110011001100110011001100110011001101 !
! !
!0011111111111110011001100110011001100110011001100110011001100110 !
! !
!0100000000000000000000000000000000000000000000000000000000000000 !

>
> So, the discussion holds on the criterion according to which trailing 
> zeros must be displayed or not.
>
>  1. I am wondering about the following, clearly without definitive
>     opinion. Just a thought:
>
>     After format(10), 1.7000000 is displayed if the NEXT figure is not
>     0, and 1.7 is displayed otherwise.
>     In other words, this would no longer refer to %eps but to the
>     format's length.
>     The issue with this proposal is that we don't have the current
>     format in mind. If all numbers are displayed in a compact form, we
>     don't see the display accuracy..
>
>     The choice to refer either to %eps or to format() could be
>     proposed through the preferences.
>
>  2. Instead, the discussion could also be about the IEEE rounding
>     mode. In some occasion, the IEEE rounding mode below %eps has
>     visible effects on results (there is something about this in
>     Bugzilla on mailing lists...). Now, i guess that testing with a
>     hardcoded equivalent of nearfloat() would be too time-consuming.
>
>
>
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-- 
Stéphane Mottelet
Ingénieur de recherche
EA 4297 Transformations Intégrées de la Matière Renouvelable
Département Génie des Procédés Industriels
Sorbonne Universités - Université de Technologie de Compiègne
CS 60319, 60203 Compiègne cedex
Tel : +33(0)344234688
http://www.utc.fr/~mottelet

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