2014-04-09 20:16 GMT+02:00 Nicolas Cellier <
nicolas.cellier.aka.nice at gmail.com>:

>
> 2014-04-09 17:53 GMT+02:00 Chris Muller <asqueaker at gmail.com>:
>
> It's just a different printOn: method.  The new one shows the "truth".
>>  You must now use one of the print formatting methods to display
>> pretty Floats.
>>
>> On Wed, Apr 9, 2014 at 10:07 AM, Vaidotas Didžbalis <vaidasd at gmail.com>
>> wrote:
>> > 1245 *  0.01 evaluates to 12.45 in Squeak 4.3, but it is
>> > 12.450000000000001 in later versions.
>> > regatds,
>> > Vaidotas
>> >
>>
>>
> Every two different Float shall have a different printString:
> (12.45) = (1245*0.01) -> false.
> So...
>
> The printString shall be the shortest decimal that rounds to the same
> float.
> It's hard to demonstrate with a simple snippet, but you can check that we
> are very close yet:
> ((Fraction readFrom: '12.450000000000001') - (1245*0.01) asTrueFraction) /
> (1245*0.01) ulp.
> ((Fraction readFrom: '12.45') - (1245*0.01) asTrueFraction) / (1245*0.01)
> ulp.
>
>
>
Maybe some other usefull expressions:

((1245*0.01) asTrueFraction printShowingMaxDecimalPlaces: Float precision -
Float emin + 1)
-> '12.4500000000000010658141036401502788066864013671875'

"Find least number of decimals necessary for converting back to the same
float"
((1 to: Float precision - Float emin + 1) detect: [:i | ((1245*0.01)
asTrueFraction roundTo: (10 raisedTo: i) reciprocal) asFloat = (1245*0.01)])
-> 15

"A variant..."
((1 to: Float precision - Float emin + 1) detect: [:i | (((1245*0.01)
asTrueFraction roundTo: (10 raisedTo: i) reciprocal) - (1245*0.01)
asTrueFraction) abs <= ((1245*0.01) ulp / 2)])
-> 15

((1245*0.01) asTrueFraction printShowingDecimalPlaces: 15)
 '12.450000000000001'
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