2014-04-09 17:53 GMT+02:00 Chris Muller asqueaker@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@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.

2014-04-09 22:23 GMT+02:00 Nicolas Cellier < nicolas.cellier.aka.nice@gmail.com>:

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

...

2014-04-09 17:53 GMT+02:00 Chris Muller asqueaker@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@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'

Ah, and of course, don't forget those ones:

(12.45 asTrueFraction printShowingMaxDecimalPlaces: Float precision - Float emin + 1) -> '12.449999999999999289457264239899814128875732421875'

so:

12.45s2 = 12.45 -> false

Float are represented in binary internally, not decimals, so every conversion binary <-> decimal might be inexact (and most often is).