Float differences

> Hi,
>
> The following code
>
> ((-10 to: 10) collect: [ :each | each * Float pi ])
> =
> ((((-10 to: 10) collect: [ :each | each * Float pi ])
> collect: [ :each | each asString])
> collect: [ :each | Float readFrom: each ])
>
> returns true on Pharo 1.4 and false on Squeak 4.3
> Some of the Floats in the array compare equal, some not.
>
> Similary, (10 raisedTo: -100) asFloat
>
> prints as '1.0e-100' in Pharo and as ' 9.99999999999999e-101' in Squeak.
>
> I know that comparing Floats on equality is often dangerous and that #closeTo: is better.
> But I would like to understand how there could be such a difference between the two.

>
> On 25.04.2012, at 13:20, Sven Van Caekenberghe wrote:
>
>> Hi,
>>
>> The following code
>>
>> ((-10 to: 10) collect: [ :each | each * Float pi ])
>> =
>> ((((-10 to: 10) collect: [ :each | each * Float pi ])
>>       collect: [ :each | each asString])
>>               collect: [ :each | Float readFrom: each ])
>>
>> returns true on Pharo 1.4 and false on Squeak 4.3
>> Some of the Floats in the array compare equal, some not.
>>
>> Similary, (10 raisedTo: -100) asFloat
>>
>> prints as '1.0e-100' in Pharo and as ' 9.99999999999999e-101' in Squeak.
>>
>> I know that comparing Floats on equality is often dangerous and that #closeTo: is better.
>> But I would like to understand how there could be such a difference between the two.
>
> If you use storeString instead of asString it will be the same. E.g.
>
>        (10 raisedTo: -100) asFloat storeString
>        ==> '1.0e-100'
>
> - Bert -
>
>
>

> Bert,
>
> On 25 Apr 2012, at 22:28, Bert Freudenberg wrote:
>
>> If you use storeString instead of asString it will be the same. E.g.
>>
>>       (10 raisedTo: -100) asFloat storeString
>>       ==> '1.0e-100'
>
> Strange, Float>>#printOn:base: uses #absPrintOn:base: in Squeak, while it uses #absPrintExactlyOn:base: in Pharo.
>
> Did Squeak make that choice for speed reasons then ?
>
> Sven

>
> On 25.04.2012, at 13:38, Nicolas Cellier wrote:
>
>> Yes, Pharo is a bit ahead, I have a change in Squeak/inbox to align
>> Squeak printing...
>>
>> Nicolas
>
> Defaulting to be right seems better than being fast ...
>
> - Bert -
>
>
>
>

> http://lists.squeakfoundation.org/pipermail/squeak-dev/2011-November/161915.html
> http://lists.squeakfoundation.org/pipermail/squeak-dev/2011-November/161916.html
>
> Le 25 avril 2012 22:49, Bert Freudenberg <[hidden email]> a écrit :
>>
>> On 25.04.2012, at 13:38, Nicolas Cellier wrote:
>>
>>> Yes, Pharo is a bit ahead, I have a change in Squeak/inbox to align
>>> Squeak printing...
>>>
>>> Nicolas
>>
>> Defaulting to be right seems better than being fast ...
>>
>> - Bert -

>
> On 25.04.2012, at 14:01, Nicolas Cellier wrote:
> >
> > Le 25 avril 2012 22:49, Bert Freudenberg <[hidden email]> a ?crit :
> >>
> >> On 25.04.2012, at 13:38, Nicolas Cellier wrote:
> >>
> >>> Yes, Pharo is a bit ahead, I have a change in Squeak/inbox to align
> >>> Squeak printing...
> >>>
> >>> Nicolas
> >>
> >> Defaulting to be right seems better than being fast ...
> >>
> >> - Bert -
> >
> > http://lists.squeakfoundation.org/pipermail/squeak-dev/2011-November/161915.html
> > http://lists.squeakfoundation.org/pipermail/squeak-dev/2011-November/161916.html
>
> Well, push it :)
>
> - Bert -
>