Squeak-dev July 1999

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367 discussions

RE: [bug] my first squeak bugfix - Interval>>includes:
by Jarvis, Robert P. 30 Jul '99

30 Jul '99

I don't think that's necessarily true. Intervals work fine with non-integer start, stop, and increment values - but if you're using Floats you must beware of roundoff errors. Try inspecting (0.1 to: 1.0 by: 0.1) asOrderedCollection and view the results. The values appear correct - but if you evaluate ((0.1 to: 1.0 by: 0.1) asOrderedCollection at: 9) - 0.9 you get -1.110223024625156e-16, indicating that some roundoff error has begun to creep in. Floats suck. Bob Jarvis The Timken Company > -----Original Message----- > From: Peter Smet [SMTP:peter.smet@flinders.edu.au] > Sent: Friday, July 30, 1999 2:40 AM > To: squeak(a)cs.uiuc.edu > Subject: Re: [bug] my first squeak bugfix - Interval>>includes: > > Sorry, > > I just looked at the Interval creation method, > and see that increment must be an Integer. > Ignore my previous posts (blush)(although it would > be nice if intervals could have smaller steps).. > > Peter > >

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RE: [bug] my first squeak bugfix - Interval>>includes:
by Jarvis, Robert P. 30 Jul '99

30 Jul '99

It looks like the examples which you expect to evaluate to true are being affected by floating point roundoff errors. In particular (((1.3 to: 2.2 by: 0.3) collect: [:i | i]) at: 3) = 1.9 evaluates to false (although ((1.3 to: 2.2 by: 0.3) at: 3) = 1.9 evaluates to true :-). If you evaluate (((1.3 to: 2.2 by: 0.3) collect: [:i | i]) at: 3) - 1.9 you get a result of 2.220446049250313e-16, so it looks like some roundoff errors are definitely creeping in. The bottom line is that you can't count on comparing two floating point values, at least one of which is a non-literal value, and expect them to be equal no matter how minor the computations involving them have been. The desired results can be obtained if by using Fractions instead of Floats. Try evaluating (13/10 to: 22/10 by: 3/10) includes: 19/10 (1 to: 5 by: 2/10) includes: 1.2 (1 to: 5 by: 3/10) includes: 1.3 which are equivalent to your expressions, but use Fractions in the appropriate places. Granted, calculations using Fractions are likely to be slower than using Floats, which may be a consideration; however, getting the wrong answer quickly is no great blessing. I hope this helps. Bob Jarvis The Timken Company > -----Original Message----- > From: Peter Smet [SMTP:peter.smet@flinders.edu.au] > Sent: Friday, July 30, 1999 2:16 AM > To: squeak(a)cs.uiuc.edu > Subject: Re: [bug] my first squeak bugfix - Interval>>includes: > > Alan, > > I was having a look at a similar fix when you posted your code. > I think it may not always work due to the nature of \\ and floating > point precision/rounding. Here are some anomalies: > (1 to: 5 by: 1) includes: 1.4 -- is true, but should be false > (1.3 to: 2.2 by: 0.3) includes: 1.9 -- is false but should be true > (1 to: 5 by: 0.2) includes: 1.2 > (1 to: 5 by: 0.3) includes: 1.3 > both (incorrectly) evaluate to false... > > Peter > > > > -----Original Message----- > From: Alan Lovejoy <sourcery(a)pacbell.net> > To: Randal L. Schwartz <merlyn(a)stonehenge.com>; squeak(a)cs.uiuc.edu > <squeak(a)cs.uiuc.edu> > Date: Friday, July 30, 1999 3:24 PM > Subject: re: [bug] my first squeak bugfix - Interval>>includes: > > > >> ** Original Sender: merlyn(a)stonehenge.com (Randal L. Schwartz) > >> > >> Interval>>includes: fails if the increment is not 1. Here's code that > works: > >> > >> includes: aNumber > >> ^self increment = 1 > >> ifTrue: [aNumber between: self first and: self last] > >> ifFalse: [super includes: aNumber] "fall back to enumerate items" > >> > > > >Oh dear. The ParcPlace code for Interval>includes: has worked since I > first > >started using it, way back in 1986. So I was shocked to see the > following > code > >in my Squeak image: > > > >Interval>includes: aNumber > > ^ aNumber between: self first and: self last > > > >I guess this reinforces for me yet again that I should not assume that > >things that have always been working correctly in the ParcPlace > >image line are also good in Squeak (in spite of the fact that they both > >ultimately come from Xerox PARC stock). > > > >As for the fix above, it will work, but I would like to offer an > alternative: > > > >Interval>includes: aNumber > > ^ (aNumber between: self first and: self last) > > and: [self increment = 1 > > ifTrue: [true] > > ifFalse: [aNumber - self first \\ self increment = 0]] > > > >Kudos to Randy for finding this! > > > >--Alan > >

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Re: [bug] my first squeak bugfix - Interval>>includes:
by Peter Smet 30 Jul '99

30 Jul '99

Sorry, I just looked at the Interval creation method, and see that increment must be an Integer. Ignore my previous posts (blush)(although it would be nice if intervals could have smaller steps).. Peter

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Re: [bug] my first squeak bugfix - Interval>>includes:
by Peter Smet 30 Jul '99

30 Jul '99

The other anomaly is: (1.5 to: 10.5 by: 1) includes: 5 which all fixes seem to wrongly evaluate to true. This is turning out to be more tricky than it first appears! Peter

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Re: [bug] my first squeak bugfix - Interval>>includes:
by Peter Smet 30 Jul '99

30 Jul '99

Alan, I was having a look at a similar fix when you posted your code. I think it may not always work due to the nature of \\ and floating point precision/rounding. Here are some anomalies: (1 to: 5 by: 1) includes: 1.4 -- is true, but should be false (1.3 to: 2.2 by: 0.3) includes: 1.9 -- is false but should be true (1 to: 5 by: 0.2) includes: 1.2 (1 to: 5 by: 0.3) includes: 1.3 both (incorrectly) evaluate to false... Peter -----Original Message----- From: Alan Lovejoy <sourcery(a)pacbell.net> To: Randal L. Schwartz <merlyn(a)stonehenge.com>; squeak(a)cs.uiuc.edu <squeak(a)cs.uiuc.edu> Date: Friday, July 30, 1999 3:24 PM Subject: re: [bug] my first squeak bugfix - Interval>>includes: >> ** Original Sender: merlyn(a)stonehenge.com (Randal L. Schwartz) >> >> Interval>>includes: fails if the increment is not 1. Here's code that works: >> >> includes: aNumber >> ^self increment = 1 >> ifTrue: [aNumber between: self first and: self last] >> ifFalse: [super includes: aNumber] "fall back to enumerate items" >> > >Oh dear. The ParcPlace code for Interval>includes: has worked since I first >started using it, way back in 1986. So I was shocked to see the following code >in my Squeak image: > >Interval>includes: aNumber > ^ aNumber between: self first and: self last > >I guess this reinforces for me yet again that I should not assume that >things that have always been working correctly in the ParcPlace >image line are also good in Squeak (in spite of the fact that they both >ultimately come from Xerox PARC stock). > >As for the fix above, it will work, but I would like to offer an alternative: > >Interval>includes: aNumber > ^ (aNumber between: self first and: self last) > and: [self increment = 1 > ifTrue: [true] > ifFalse: [aNumber - self first \\ self increment = 0]] > >Kudos to Randy for finding this! > >--Alan >

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[bug] my first squeak bugfix - Interval>>includes:
by merlyn＠stonehenge.com 30 Jul '99

30 Jul '99

Interval>>includes: fails if the increment is not 1. Here's code that works: includes: aNumber ^self increment = 1 ifTrue: [aNumber between: self first and: self last] ifFalse: [super includes: aNumber] "fall back to enumerate items" -- Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095 <merlyn(a)stonehenge.com> <URL:http://www.stonehenge.com/merlyn/> Perl/Unix/security consulting, Technical writing, Comedy, etc. etc. See PerlTraining.Stonehenge.com for onsite and open-enrollment Perl training!

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Re: Smalltalk implementation of Linda?
by Benoit St-Jean 30 Jul '99

30 Jul '99

At 08:57 99-07-29 -0800, you wrote: >Hello - > >I'm looking for a non-proprietary Smalltalk impementation of the Linda tuple-space kernel for parallel programming. We are considering this facility for Squeak and it would be nice to save a little work. > >If you don't know about Linda and are curious, check out CACM Vol 32 no. 4, April 1989. Wasn't it the C subset (for parallell programming) used in the first versions of StarSocrates chess program? ___________________________________ Benoit St-Jean Creative Technologies International lamneth(a)aei.ca (514) 871-8585 #234

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RE: [SqT][BUG][FIX] spawn hierarchy causing "subscript is out of bounds:"
by Norton, Chris 30 Jul '99

30 Jul '99

Hi Folks. Test pilot Chris Norton reporting for duty... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > Dwight Hughes [SMTP:dwighth@ipa.net] wrote: "I'm seeing this in various classes in the System Browser. I'm selecting a class, then "-- all --" or a method category, then a method, then going back to the class and doing a "spawn hierarchy". I'm giving the method protocol because the problem seems to be grouped this way (but the same methods will give the same error even when "-- all --" is selected) -- the index matches the selector's position in the list for its category." ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I'm pretty sure I've got this fixed, but I'm in the middle of a major release and I'm up to my eyeballs in work. So I'll toss out this fix to y'all and hope for the best. ;-) Actually, I'm pretty confident that this fixes Dwight's reported bug. However, as with all new code, a period of general testing should really occur prior to release of this fix. So without further ado, here's my fix. Test pilots only. Cheers! ---==> Chris <<Spawn Hierarchy Fix.29Jul703pm.cs>> Content-Type: application/octet-stream; name="Spawn Hierarchy Fix.29Jul703pm.cs" Content-Disposition: attachment; filename="Spawn Hierarchy Fix.29Jul703pm.cs" Attachment converted: Anon:Spawn Hierarchy Fix.29Jul703pm. (????/----) (00012177)

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RE: Why set identity of #becomeForward: argument to the receiver?
by Raab, Andreas 30 Jul '99

30 Jul '99

> The upshot of this is if I had created an IdentityDictionary before the > #becomeForward, such as > > (C := IdentityDictionary new) > at: A put: 1; > at: B put: 2. > > Then after the #becomeForward: I find > (C at: A) = 1 > (C at: B) = 1 > > I would have imagined that after the #becomeForward: that A would now take > the original #identityHash value of B. So > > (C at: A) = 2 > (C at: B) = 2 > Well - first of all, after the #becomeForward: operation you'll have two identical keys in the Dictionary (meaning that your Dictionary is screwed up anyways). Whose's value you'll get depends on what is found first in the Dictionary; and if there has been any collision between A and B before you did your #becomeForward: operation you'll get the value of the first (which is '1' in your above example) since that association is in the right place for the key. If there hasn't been a collision you should get the value of the second one - so just have your code run often enough and you'll get different results. BTW, how do proxies deal with this issue?! Do they generally keep an ID hash for the external object around?! Andreas -- +===== Andreas Raab ========= (andreasr(a)wdi.disney.com) ==+ | Walt Disney Imagineering Phone: +1 818 544 5016 I I Glendale, CA Fax: +1 818 544 4544 I +======< http://isgwww.cs.uni-magdeburg.de/~raab >========+

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Re: Celeste attachments handling improvements?
by mdr＠scn.org 29 Jul '99

29 Jul '99

"Lex Spoon" <lex(a)cc.gatech.edu> wrote: > Look at the popup menu in the top-right pane page--isn't there a "save message" option? > That's how I've been using to handle MIME attachments I receive. [...] Totally neat - I got my test attachment! I had to use a slightly different process to do this in Netscape Communicator mail: (1) create a category (2) use "file" to make a copy of the message in the category (3) use "export category (Unix/Eudora)" (which works on the whole category) (4) import the eudora mailbox into Communicator, see the attachment and be happy! Mike

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