[Scilab-users] {EXT} Re: display of complex/not real numbers, again

[Dang Ngoc Chan, Christophe]

Hello,

> De : Stéphane Mottelet
> Envoyé : vendredi 13 septembre 2019 14:23
>
> I think that we do agree about the fact that the actual Scilab display
> [...]
> --> x(8)
> ans  =
>
>   1.7
> --> x(8)-1.7
> ans  =
>
>   2.220D-16
> is pretty but not correct/homogeneous/honest

I don't agree about this.
The decimal number can only rarely be represented exactly in binary according to IEEE 754.

This means that there should always be trailing zeros to highlight the fact that there is a 10^-16 discrepancy between the stored value and the displayed value?
I don't find this convenient.

The fact that some people are not aware of this discrepancy can be a problem but it is the general problem of underflow or subtractive cancellation or round-off error etc.

The problem is not less important than ignoring a number is complex with a zero imaginary part, but I'm not sure it can be handled in the same way.

--
Christophe Dang Ngoc Chan
Mechanical calculation engineer

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