July 2014 - Pharo-dev - lists.pharo.org

Re: [Pharo-dev] Division isn't correct

by Camille Teruel

On 11 juil. 2014, at 17:01, Igor Stasenko <siguctua(a)gmail.com> wrote: > I would put it this way: > - If you writing code, which requires comparing two floating-point values for equality, then you do something wrong. :D Rule of thumb: don't use floats ;) > > -- > Best regards, > Igor Stasenko.

July 11, 2014

Re: [Pharo-dev] Division isn't correct

by Esteban A. Maringolo

2014-07-11 12:02 GMT-03:00 Natalia Tymchuk <natalia.tymchuk(a)unikernel.net>: > But why > 185/10 = 18.5 -> true? It is not deterministic. That's why you can't rely on such comparisons. Regards!

July 11, 2014

Re: [Pharo-dev] Division isn't correct

by Natalia Tymchuk

But why 185/10 = 18.5 -> true? On Jul 11, 2014, at 4:40 PM, Norbert Hartl <norbert(a)hartl.name> wrote: > > Am 11.07.2014 um 16:33 schrieb Yuriy Tymchuk <yuriy.tymchuk(a)me.com>: > >> >> On 11 Jul 2014, at 16:30, Esteban Lorenzano <estebanlm(a)gmail.com> wrote: >> >>> On 11 Jul 2014, at 16:22, kilon alios <kilon.alios(a)gmail.com> wrote: >>> >>>> why not round it before comparing it ? looks like an easy enough problem to fix . I would expect that to be equal. >>> >>> because it wouldnât be correct :) >> >> But then why 4/2 = 2? > > The same reason why > > 4/3 = 8/6 > > :) > > Norbert >> >>> >>>> >>>> >>>> On Fri, Jul 11, 2014 at 5:18 PM, Yuriy Tymchuk <yuriy.tymchuk(a)me.com> wrote: >>>> Thatâs why mathematics and programming are two different thingsâ¦ >>>> >>>> >>>> On 11 Jul 2014, at 16:08, Esteban A. Maringolo <emaringolo(a)gmail.com> wrote: >>>> >>>> > Usually comparing against floats is not as deterministic as you would >>>> > expect. And in other dialects you use #equals: instead of #= >>>> > >>>> > But in Pharo there is no #equals: and instead there is a #closeTo:, >>>> > but #closeTo: has an arbitrary decimal precision, more than enough for >>>> > commong arithmetic. >>>> > >>>> > Regards! >>>> > >>>> > Esteban A. Maringolo >>>> > >>>> > >>>> > 2014-07-11 10:59 GMT-03:00 Goubier Thierry <thierry.goubier(a)cea.fr>: >>>> >> :) >>>> >> >>>> >> in Smalltalk, the division of two integers is a fraction, not a float. >>>> >> >>>> >> i.e. 1/5 is 1/5. >>>> >> >>>> >> Thierry >>>> >> >>>> >> Le 11/07/2014 15:53, Natalia Tymchuk a Ã©crit : >>>> >>> >>>> >>> Hello. >>>> >>> I found interesting thing: >>>> >>> Why it is like this? >>>> >>> >>>> >>> Best regards, >>>> >>> Natalia >>>> >>> >>>> >> >>>> >> -- >>>> >> Thierry Goubier >>>> >> CEA list >>>> >> Laboratoire des Fondations des SystÃ¨mes Temps RÃ©el EmbarquÃ©s >>>> >> 91191 Gif sur Yvette Cedex >>>> >> France >>>> >> Phone/Fax: +33 (0) 1 69 08 32 92 / 83 95 >>>> >> >>>> > >>>> >>>> >>>> >>> >> >

July 11, 2014

Re: [Pharo-dev] Division isn't correct

by Igor Stasenko

I would put it this way: - If you writing code, which requires comparing two floating-point values for equality, then you do something wrong. -- Best regards, Igor Stasenko.

July 11, 2014

Re: [Pharo-dev] Division isn't correct

by Norbert Hartl

Am 11.07.2014 um 16:33 schrieb Yuriy Tymchuk <yuriy.tymchuk(a)me.com>: > > On 11 Jul 2014, at 16:30, Esteban Lorenzano <estebanlm(a)gmail.com> wrote: > >> On 11 Jul 2014, at 16:22, kilon alios <kilon.alios(a)gmail.com> wrote: >> >>> why not round it before comparing it ? looks like an easy enough problem to fix . I would expect that to be equal. >> >> because it wouldnât be correct :) > > But then why 4/2 = 2? The same reason why 4/3 = 8/6 :) Norbert > >> >>> >>> >>> On Fri, Jul 11, 2014 at 5:18 PM, Yuriy Tymchuk <yuriy.tymchuk(a)me.com> wrote: >>> Thatâs why mathematics and programming are two different thingsâ¦ >>> >>> >>> On 11 Jul 2014, at 16:08, Esteban A. Maringolo <emaringolo(a)gmail.com> wrote: >>> >>> > Usually comparing against floats is not as deterministic as you would >>> > expect. And in other dialects you use #equals: instead of #= >>> > >>> > But in Pharo there is no #equals: and instead there is a #closeTo:, >>> > but #closeTo: has an arbitrary decimal precision, more than enough for >>> > commong arithmetic. >>> > >>> > Regards! >>> > >>> > Esteban A. Maringolo >>> > >>> > >>> > 2014-07-11 10:59 GMT-03:00 Goubier Thierry <thierry.goubier(a)cea.fr>: >>> >> :) >>> >> >>> >> in Smalltalk, the division of two integers is a fraction, not a float. >>> >> >>> >> i.e. 1/5 is 1/5. >>> >> >>> >> Thierry >>> >> >>> >> Le 11/07/2014 15:53, Natalia Tymchuk a Ã©crit : >>> >>> >>> >>> Hello. >>> >>> I found interesting thing: >>> >>> Why it is like this? >>> >>> >>> >>> Best regards, >>> >>> Natalia >>> >>> >>> >> >>> >> -- >>> >> Thierry Goubier >>> >> CEA list >>> >> Laboratoire des Fondations des SystÃ¨mes Temps RÃ©el EmbarquÃ©s >>> >> 91191 Gif sur Yvette Cedex >>> >> France >>> >> Phone/Fax: +33 (0) 1 69 08 32 92 / 83 95 >>> >> >>> > >>> >>> >>> >> >

July 11, 2014

Re: [Pharo-dev] Division isn't correct

by Yuriy Tymchuk

On 11 Jul 2014, at 16:30, Esteban Lorenzano <estebanlm(a)gmail.com> wrote: > On 11 Jul 2014, at 16:22, kilon alios <kilon.alios(a)gmail.com> wrote: > >> why not round it before comparing it ? looks like an easy enough problem to fix . I would expect that to be equal. > > because it wouldnât be correct :) But then why 4/2 = 2? > >> >> >> On Fri, Jul 11, 2014 at 5:18 PM, Yuriy Tymchuk <yuriy.tymchuk(a)me.com> wrote: >> Thatâs why mathematics and programming are two different thingsâ¦ >> >> >> On 11 Jul 2014, at 16:08, Esteban A. Maringolo <emaringolo(a)gmail.com> wrote: >> >> > Usually comparing against floats is not as deterministic as you would >> > expect. And in other dialects you use #equals: instead of #= >> > >> > But in Pharo there is no #equals: and instead there is a #closeTo:, >> > but #closeTo: has an arbitrary decimal precision, more than enough for >> > commong arithmetic. >> > >> > Regards! >> > >> > Esteban A. Maringolo >> > >> > >> > 2014-07-11 10:59 GMT-03:00 Goubier Thierry <thierry.goubier(a)cea.fr>: >> >> :) >> >> >> >> in Smalltalk, the division of two integers is a fraction, not a float. >> >> >> >> i.e. 1/5 is 1/5. >> >> >> >> Thierry >> >> >> >> Le 11/07/2014 15:53, Natalia Tymchuk a Ã©crit : >> >>> >> >>> Hello. >> >>> I found interesting thing: >> >>> Why it is like this? >> >>> >> >>> Best regards, >> >>> Natalia >> >>> >> >> >> >> -- >> >> Thierry Goubier >> >> CEA list >> >> Laboratoire des Fondations des SystÃ¨mes Temps RÃ©el EmbarquÃ©s >> >> 91191 Gif sur Yvette Cedex >> >> France >> >> Phone/Fax: +33 (0) 1 69 08 32 92 / 83 95 >> >> >> > >> >> >> >

July 11, 2014

Re: [Pharo-dev] Division isn't correct

by Esteban Lorenzano

On 11 Jul 2014, at 16:22, kilon alios <kilon.alios(a)gmail.com> wrote: > why not round it before comparing it ? looks like an easy enough problem to fix . I would expect that to be equal. because it wouldnât be correct :) > > > On Fri, Jul 11, 2014 at 5:18 PM, Yuriy Tymchuk <yuriy.tymchuk(a)me.com> wrote: > Thatâs why mathematics and programming are two different thingsâ¦ > > > On 11 Jul 2014, at 16:08, Esteban A. Maringolo <emaringolo(a)gmail.com> wrote: > > > Usually comparing against floats is not as deterministic as you would > > expect. And in other dialects you use #equals: instead of #= > > > > But in Pharo there is no #equals: and instead there is a #closeTo:, > > but #closeTo: has an arbitrary decimal precision, more than enough for > > commong arithmetic. > > > > Regards! > > > > Esteban A. Maringolo > > > > > > 2014-07-11 10:59 GMT-03:00 Goubier Thierry <thierry.goubier(a)cea.fr>: > >> :) > >> > >> in Smalltalk, the division of two integers is a fraction, not a float. > >> > >> i.e. 1/5 is 1/5. > >> > >> Thierry > >> > >> Le 11/07/2014 15:53, Natalia Tymchuk a Ã©crit : > >>> > >>> Hello. > >>> I found interesting thing: > >>> Why it is like this? > >>> > >>> Best regards, > >>> Natalia > >>> > >> > >> -- > >> Thierry Goubier > >> CEA list > >> Laboratoire des Fondations des SystÃ¨mes Temps RÃ©el EmbarquÃ©s > >> 91191 Gif sur Yvette Cedex > >> France > >> Phone/Fax: +33 (0) 1 69 08 32 92 / 83 95 > >> > > > > >

July 11, 2014

Re: [Pharo-dev] Division isn't correct

by kilon alios

why not round it before comparing it ? looks like an easy enough problem to fix . I would expect that to be equal. On Fri, Jul 11, 2014 at 5:18 PM, Yuriy Tymchuk <yuriy.tymchuk(a)me.com> wrote: > Thatâs why mathematics and programming are two different thingsâ¦ > > > On 11 Jul 2014, at 16:08, Esteban A. Maringolo <emaringolo(a)gmail.com> > wrote: > > > Usually comparing against floats is not as deterministic as you would > > expect. And in other dialects you use #equals: instead of #= > > > > But in Pharo there is no #equals: and instead there is a #closeTo:, > > but #closeTo: has an arbitrary decimal precision, more than enough for > > commong arithmetic. > > > > Regards! > > > > Esteban A. Maringolo > > > > > > 2014-07-11 10:59 GMT-03:00 Goubier Thierry <thierry.goubier(a)cea.fr>: > >> :) > >> > >> in Smalltalk, the division of two integers is a fraction, not a float. > >> > >> i.e. 1/5 is 1/5. > >> > >> Thierry > >> > >> Le 11/07/2014 15:53, Natalia Tymchuk a Ã©crit : > >>> > >>> Hello. > >>> I found interesting thing: > >>> Why it is like this? > >>> > >>> Best regards, > >>> Natalia > >>> > >> > >> -- > >> Thierry Goubier > >> CEA list > >> Laboratoire des Fondations des SystÃ¨mes Temps RÃ©el EmbarquÃ©s > >> 91191 Gif sur Yvette Cedex > >> France > >> Phone/Fax: +33 (0) 1 69 08 32 92 / 83 95 > >> > > > > >

July 11, 2014

Re: [Pharo-dev] Division isn't correct

by Yuriy Tymchuk

Thatâs why mathematics and programming are two different thingsâ¦ On 11 Jul 2014, at 16:08, Esteban A. Maringolo <emaringolo(a)gmail.com> wrote: > Usually comparing against floats is not as deterministic as you would > expect. And in other dialects you use #equals: instead of #= > > But in Pharo there is no #equals: and instead there is a #closeTo:, > but #closeTo: has an arbitrary decimal precision, more than enough for > commong arithmetic. > > Regards! > > Esteban A. Maringolo > > > 2014-07-11 10:59 GMT-03:00 Goubier Thierry <thierry.goubier(a)cea.fr>: >> :) >> >> in Smalltalk, the division of two integers is a fraction, not a float. >> >> i.e. 1/5 is 1/5. >> >> Thierry >> >> Le 11/07/2014 15:53, Natalia Tymchuk a Ã©crit : >>> >>> Hello. >>> I found interesting thing: >>> Why it is like this? >>> >>> Best regards, >>> Natalia >>> >> >> -- >> Thierry Goubier >> CEA list >> Laboratoire des Fondations des SystÃ¨mes Temps RÃ©el EmbarquÃ©s >> 91191 Gif sur Yvette Cedex >> France >> Phone/Fax: +33 (0) 1 69 08 32 92 / 83 95 >> >

July 11, 2014

Re: [Pharo-dev] Division isn't correct

by Esteban A. Maringolo

Usually comparing against floats is not as deterministic as you would expect. And in other dialects you use #equals: instead of #= But in Pharo there is no #equals: and instead there is a #closeTo:, but #closeTo: has an arbitrary decimal precision, more than enough for commong arithmetic. Regards! Esteban A. Maringolo 2014-07-11 10:59 GMT-03:00 Goubier Thierry <thierry.goubier(a)cea.fr>: > :) > > in Smalltalk, the division of two integers is a fraction, not a float. > > i.e. 1/5 is 1/5. > > Thierry > > Le 11/07/2014 15:53, Natalia Tymchuk a Ã©crit : >> >> Hello. >> I found interesting thing: >> Why it is like this? >> >> Best regards, >> Natalia >> > > -- > Thierry Goubier > CEA list > Laboratoire des Fondations des SystÃ¨mes Temps RÃ©el EmbarquÃ©s > 91191 Gif sur Yvette Cedex > France > Phone/Fax: +33 (0) 1 69 08 32 92 / 83 95 >

July 11, 2014