The Inbox: Kernel-mtf.924.mcz
Locked
 
|
A new version of Kernel was added to project The Inbox:
http://source.squeak.org/inbox/Kernel-mtf.924.mcz ==================== Summary ==================== Name: Kernel-mtf.924 Author: mtf Time: 2 May 2015, 12:26:05.675 pm UUID: 7f688860-5202-4c0d-8ece-8723fe7317d6 Ancestors: Kernel-nice.923 Copied Number >> #round: from Pharo. One of 3 methods needed to make the Artefact pdf library work on squeak: https://sites.google.com/site/artefactpdf/ =============== Diff against Kernel-nice.923 =============== Item was added: + ----- Method: Float>>round: (in category 'truncation and round off') ----- + round: numberOfWishedDecimal + "only leave a fixed amount of decimal" + "10.12345 round: 2 => 10.12" + + | v | + v := 10 raisedTo: numberOfWishedDecimal. + ^ ((self * v) rounded / v) asFloat + ! Item was added: + ----- Method: Fraction>>round: (in category 'truncation and round off') ----- + round: numberOfWishedDecimal + ^self asFloat round: numberOfWishedDecimal! Item was added: + ----- Method: Integer>>round: (in category 'truncation and round off') ----- + round: numberOfWishedDecimal + ^self! Item was added: + ----- Method: Number>>round: (in category 'truncation and round off') ----- + round: numberOfWishedDecimal + self subclassResponsibility! |
Re: The Inbox: Kernel-mtf.924.mcz
|
|
2015-05-02 18:27 GMT+02:00 <[hidden email]>: If it's subclass responsibility, then it must be implemented in ScaledDecimal.A new version of Kernel was added to project The Inbox: self assert: (Float fmax round: 2) = Float fmax. It's probably not very important for artefact, but if this method has a wider usage than artefact, then it should better be robust to overflow... Item was added: Transforming exact arithmetic into inexact Float sounds like heresy to me ;) That's a questionable choice. Why this cult to Float would be necessary here? Item was added: This is not necessary in Pharo, because ScaledDecimal has been moved under Fraction, but it is in Squeak. I'd rather see Float implementation moved up (without the asFloat) and Float invoking super asFloat... I didn't check artefact, but I suspect that the usage is just to printShowingMaxDecimals: numberOfWishedDecimal, which would make the whole method moot. Nicolas |
Re: The Inbox: Kernel-mtf.924.mcz
|
|
On Sat, 2 May 2015, Nicolas Cellier wrote:
> > > 2015-05-02 18:27 GMT+02:00 <[hidden email]>: > A new version of Kernel was added to project The Inbox: > http://source.squeak.org/inbox/Kernel-mtf.924.mcz > > ==================== Summary ==================== > > Name: Kernel-mtf.924 > Author: mtf > Time: 2 May 2015, 12:26:05.675 pm > UUID: 7f688860-5202-4c0d-8ece-8723fe7317d6 > Ancestors: Kernel-nice.923 > > Copied Number >> #round: from Pharo. One of 3 methods needed to make the Artefact pdf library work on squeak: > https://sites.google.com/site/artefactpdf/ > > =============== Diff against Kernel-nice.923 =============== > > Item was added: > + ----- Method: Float>>round: (in category 'truncation and round off') ----- > + round: numberOfWishedDecimal > + "only leave a fixed amount of decimal" > + "10.12345 round: 2 => 10.12" > + > + | v | > + v := 10 raisedTo: numberOfWishedDecimal. > + ^ ((self * v) rounded / v) asFloat > + ! > > > self assert: (Float fmax round: 2) = Float fmax. > > It's probably not very important for artefact, but if this method has a wider usage than artefact, then it should better be robust to overflow... > > Item was added: > + ----- Method: Fraction>>round: (in category 'truncation and round off') ----- > + round: numberOfWishedDecimal > + ^self asFloat round: numberOfWishedDecimal! > > > Transforming exact arithmetic into inexact Float sounds like heresy to me ;) > That's a questionable choice. > Why this cult to Float would be necessary here? > > Item was added: > + ----- Method: Integer>>round: (in category 'truncation and round off') ----- > + round: numberOfWishedDecimal > + ^self! > > Item was added: > + ----- Method: Number>>round: (in category 'truncation and round off') ----- > + round: numberOfWishedDecimal > + self subclassResponsibility! > > > If it's subclass responsibility, then it must be implemented in ScaledDecimal. > This is not necessary in Pharo, because ScaledDecimal has been moved under Fraction, but it is in Squeak. > I'd rather see Float implementation moved up (without the asFloat) and Float invoking super asFloat... > > I didn't check artefact, but I suspect that the usage is just to printShowingMaxDecimals: numberOfWishedDecimal, which would make the whole method > moot. You're right about the printing thing in Artefact. I replaced #round: with #printOn:maxDecimalPlaces: in my image. Levente > > Nicolas > > |
Re: The Inbox: Kernel-mtf.924.mcz
|
|
2015-05-02 22:32 GMT+02:00 Levente Uzonyi <[hidden email]>:
No, this is because 'x roundTo: (10 raisedTo: n) reciprocal' is a bit worse than '(x * (10 raisedTo: n) asFloat) rounded / (10 raisedTo: n) asFloat' Indeed, in the first one you perform one more inexact operation (1/100 ~= 0.01). But anyway, these are vain efforts, because #round: in Pharo still cumulates several inexact operations and thus will sometimes fail to deliver the correct answer. For example: self assert: 1.0005 < (5/10000+1) ==> ((1.0005 round: 3) = 1). alas, it answers 1.001 and differs from printShowingMaxDecimalPlaces: 3... Definitely not top quality. I think Pharo did not integrate printShowingMaxDecimalPlaces: so that probably explains the mistake. Or maybe they were influenced by Python round, but should have checked how it is implemented: For example, see https://github.com/python/cpython/blob/c7688b44387d116522ff53c0927169db45969f0e/Python/pymath.c double round(double x) { double absx, y; absx = fabs(x); y = floor(absx); if (absx - y >= 0.5) y += 1.0; return copysign(y, x); } That should translate easily in Smalltalk if REALLY necessary... You're right about the printing thing in Artefact. I replaced #round: with #printOn:maxDecimalPlaces: in my image. Easy to guess, the only other possible use I can think of, is naive monetary apps; that makes two reasons to ban the message ;) Levente |
Re: The Inbox: Kernel-mtf.924.mcz
|
|
2015-05-02 23:04 GMT+02:00 Nicolas Cellier <[hidden email]>:
Oups, that's round without argument...
|
Re: The Inbox: Kernel-mtf.924.mcz
|
|
2015-05-02 23:10 GMT+02:00 Nicolas Cellier <[hidden email]>:
It is rather in https://github.com/python/cpython/blob/12f02a041ecca16d61352548dc4573095f0dae10/Objects/floatobject.c And it is using dtoa, that is equivalent to ^(Float readFrom: (self printShowingDecimalPlaces: n) readStream)
|
«
Return to Squeak - Dev
|
1 view|%1 views
| Free forum by Nabble | Edit this page |