On 18 Sep 2018, at 11:13, Guillermo Polito <guillermopolito@gmail.com> wrote:



On Tue, Sep 18, 2018 at 11:06 AM Julien <julien.delplanque@inria.fr> wrote:
Hello,

I realised that it is possible to create an interval of floats.

I think this is bad because, since intervals are computed by successively adding a number, it might result in precision errors.

(0.0 to: 1.0 by: 0.1) asArray >>> #(0.0 0.1 0.2 0.30000000000000004 0.4 0.5 0.6000000000000001 0.7000000000000001 0.8 0.9 1.0)

The correct (precise) way to do it would be to use ScaledDecimal:

(0.0s1 to: 1.0s1 by: 0.1s1) asArray >>> #(0.0s1 0.1s1 0.2s1 0.3s1 0.4s1 0.5s1 0.6s1 0.7s1 0.8s1 0.9s1 1.0s1)


And I���d like to discuss this with you.

What do you think?

Well, I think it's a matter of balance :)

#to:by: is defined in Number. So we could, for example, cancel it in Float.
However, people would still be able to do

1 to: 1.0 by: 0.1

Which would still show problems.

Nevertheless, I have seen this a lot of times. 

0.0 to: 1.0 by: 0.1

Is a common use case.


And moreover, we could try to do

1 to: 7 by: (Margin fromNumber: 1)

And even worse

1 to: Object new by: (Margin fromNumber: 1)

I think adding type-validations all over the place is not a good solution, and is kind of opposite to our philosophy...

So we should
 - document the good usages
 - document the bad ones
 - and live with the fact that we have a relaxed type system that will fail at runtime :)

yup. 
But not cancel.

Esteban


Guille