2016-10-26 9:14 GMT+02:00 stepharo <steph...@free.fr>:
> Hi nicolas
>
> So what is the solution? We can integrate fast a solution.
> I would really like to see them fix in Pharo 60.
> I'm writing a book for newbie and this is the third time I change one
> chapter
> so may be I should stop and throw away this chapter.
>
>
1) for Fraction:
round: numberOfWishedDecimal
v := 10 raisedTo: numberOfWishedDecimal.
^ ((self * v) rounded / v) asFloat
or just replace asFloat if you wish to remain exact:
round: numberOfWishedDecimal
v := 10 raisedTo: numberOfWishedDecimal.
^ ((self * v) rounded / v) asScaledDecimal: numberOfWishedDecimal
2) for Float, it is in 15471:
round: numberOfWishedDecimal
| v maxNumberOfDecimals |
maxNumberOfDecimals := self class precision - 1 - (self exponent max:
self class emin).
maxNumberOfDecimals < numberOfWishedDecimal ifTrue: [^self].
v := 10 raisedTo: numberOfWishedDecimal.
^ ((self asFraction * v) rounded / v) asFloat
or if Fraction already answers a Float:
round: numberOfWishedDecimal
| maxNumberOfDecimals |
maxNumberOfDecimals := self class precision - 1 - (self exponent max:
self class emin).
maxNumberOfDecimals < numberOfWishedDecimal ifTrue: [^self].
^ self asFraction round: numberOfWishedDecimal
It's slower than current implementation, but will round exactly to the
nearest Float.
It's possible to have faster implementation up to 22 decimals if you
provide a fused-multiply-accumulate primitive...
You see I'm not good in math so even if I try hard I will not have a good
> solution.
> This is the same for marcus and most people in our team.
> I reopened these issues.
>
> Stef
>
>
>
> 2016-10-25 23:22 GMT+02:00 stepharo <steph...@free.fr>:
>
>> Ok for the advice
>>
>> Now round: aNumberOfDigits seems to work fine.
>>
>> Stef
>>
>>
> No it's not, but issues are timing out too fast ;)
> https://pharo.fogbugz.com/f/cases/15471/Can-t-round-Float-
> fmax-to-2-decimal-places
> https://pharo.fogbugz.com/f/cases/15472/Fraction-rounding-
> to-n-decimal-places-is-inexact
> https://pharo.fogbugz.com/f/cases/15473/Float-round-to-n-
> decimal-places-is-not-in-agreement-with-printShowingDecimalPlaces
>
> I hate to say that, but try in python, they got it right...
>
>
>
>> Le 25/10/16 à 11:05, Henrik Johansen a écrit :
>>
>> +1.
>>
>> Unless you're dealing with fixed precision* entities, it's usually better
>> to specify digits to display in printing methods themselves
>> (#printShowingDecimalPlaces: & friends in base image).
>> As per previous discussions around this that arise every second year or
>> so, rounding the number itself (as long as we're dealing with floats) will
>> never work as you want reliably.
>>
>> Cheers,
>> Henry
>>
>> * And in that case, you'd use ScaledDecimals
>>
>> On 23 Oct 2016, at 7:08 , p...@highoctane.be wrote:
>>
>> I use the Printf package for that.
>>
>> v := 65.456.
>> 'With 2 decimal digits: %5.2f, or 3 like this: %6.3f'
>> printf: {v. v}.
>>
>> With 2 decimal digits: 65.45, or 3 like this: 65.456
>>
>> It is in http://www.smalltalkhub.com/#!/~philippeback/HOExtras
>>
>> Printf
>>
>> I am just used to C printf and well, I like the way it works.
>>
>> Phil
>>
>>
>>
>
>
