Surprise of the day

I think the issue is not whether it can be done a different way (which it can, as Paul demonstrated), but rather whether #sorted: should work for various kinds of collections. Should I have to do this?:
 
    sorted := (aCollection isKindOf: SortedCollection)
        ifTrue: [aCollection sortBlock: aBlock]
        ifFalse: [aCollection sorted: aBlock]
 
I think the argument is for consistency:
 
    sorted := aCollection sorted: aBlock
 
Dave Stevenson
dave.stevenson@...

---

From: Paul Baumann <paul.baumann@...>
To: "Joerg Beekmann, DeepCove Labs (YVR)" <joerg@...>; "vwnc@..." <vwnc@...>
Sent: Wed, August 4, 2010 1:38:27 PM
Subject: Re: [vwnc] Surprise of the day

That also errors in VW 7.5. You'd meant to do:

#(1 2 3 4) asSortedCollection: [:a :b| a > b]

Paul Baumann

---

From: vwnc-bounces@... [[hidden email]] On Behalf Of Joerg Beekmann, DeepCove Labs (YVR)
Sent: Wednesday, August 04, 2010 4:15 PM
To: vwnc@...
Subject: [vwnc] Surprise of the day

In VW7.7 sorted collections can’t be sorted. For example the following breaks.
 
#(1 2 3 4) asSortedCollection sorted: [:a :b| a > b]
 
My first take on this is that it is a bug.
 
Joerg
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Agreed. I think we took this approach in Grease, if I recall correctly (and Pharo has followed suit).

#sortBlock: is an accessor, #sorted: is a conversion method. That they would happen to have the same implementation on this class is irrelevant.

Julian

On 10-08-04 9:54 PM, "Dave Stevenson" <dave.stevenson@...> wrote:

I think the issue is not whether it can be done a different way (which it can, as Paul demonstrated), but rather whether #sorted: should work for various kinds of collections. Should I have to do this?:
 
    sorted := (aCollection isKindOf: SortedCollection)
        ifTrue: [aCollection sortBlock: aBlock]
        ifFalse: [aCollection sorted: aBlock]
 
I think the argument is for consistency:
 
    sorted := aCollection sorted: aBlock
 
Dave Stevenson
dave.stevenson@...

---

From: Paul Baumann <paul.baumann@...>
To: "Joerg Beekmann, DeepCove Labs (YVR)" <joerg@...>; "vwnc@..." <vwnc@...>
Sent: Wed, August 4, 2010 1:38:27 PM
Subject: Re: [vwnc] Surprise of the day

That also errors in VW 7.5. You'd meant to do:

#(1 2 3 4) asSortedCollection: [:a :b| a > b]

Paul Baumann

---

From: vwnc-bounces@... [[hidden email]] On Behalf Of Joerg Beekmann, DeepCove Labs (YVR)
Sent: Wednesday, August 04, 2010 4:15 PM
To: vwnc@...
Subject: [vwnc] Surprise of the day

In VW7.7 sorted collections can’t be sorted. For example the following breaks.
 
#(1 2 3 4) asSortedCollection sorted: [:a :b| a > b]
 
My first take on this is that it is a bug.
 
Joerg
-----
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DeepCove Labs
4th floor 595 Howe Street
Vancouver, BC, V6C 2T5
voice +1.604.689.0322
fax   +1.604.689.0311
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Hi Paul,

I can't argue with that. :)

Julian

----- Original Message -----
From: Paul Baumann <[hidden email]>
To: Fitzell, Julian; 'Joerg Beekmann, DeepCove Labs (YVR)' <[hidden email]>; [hidden email] <[hidden email]>
Sent: Mon Aug 09 20:32:58 2010
Subject: RE: [vwnc] Surprise of the day


>> I think it would read "Answer a sequenceable collection containing the contents of the receiver sorted according to aBlock. The receiver is not modified."

Yes, that is a better method comment.

#sorted: is broken, uncommented (at least as of VW 7.5), typically slower, and non-portable. You think #sorted: can be better than #asSortedCollection: and should be fixed instead of removed, I respect that. I see why you appreciate it. I'll stick with #asSortedCollection: until #sorted: is better.

Paul Baumann


-----Original Message-----
From: Julian Fitzell [[hidden email]]
Sent: Monday, August 09, 2010 6:03 AM
To: Paul Baumann; 'Joerg Beekmann, DeepCove Labs (YVR)'; [hidden email]
Subject: Re: [vwnc] Surprise of the day
Importance: High

On 10-08-06 4:58 PM, "Paul Baumann" <[hidden email]> wrote:
> If the purpose of #sorted: were documented, I think it would read
> "Answer a collection similar to the receiver with contents sorted according to aBlock".
> The "similar to the receiver" part is the only part that would
> distinguish it from #asSortedCollection:.

I disagree. I think it would read "Answer a sequenceable collection containing the contents of the receiver sorted according to aBlock. The receiver is not modified."

A SortedCollection is specifically implemented to allow the contents to change and to remain sorted when elements are added. If you don't need that functionality, there's no point demanding a SortedCollection. #sorted:
allows each collection to make the decision of how to most efficiently create and return the result, whether that is returning a copy of self, a copy with the sort block changed, an Array created in some fashion or other, or some other method. It's a protocol that allows you ask for something specific that you need without specifying the implementation, which is exactly what OO is supposed to be about.

Julian



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Neat! I’ve been meaning to implement sorting by multiple criteria for a while. We have something similar (unary sort criterion, block or selector), with our addition being the caching of the result of the sort criterion for each element. This can produce a useful speedup, e.g. if the sort criteria creates a string. Since we only have a single criterion we simply precalculate the sort value for each element, making an association of element->sortValue, sort the associations with a fixed sortBlock using assoc value, and then collect the keys.

 

Steve

 

From: [hidden email] [[hidden email]] On Behalf Of Dave Stevenson
Sent: 10. elokuuta 2010 1:07
To: [hidden email]
Subject: Re: [vwnc] Surprise of the day

 

Some time ago I wrote some extension methods that allow me to pass a block, a selector, or a collection of blocks/selectors for sorting (see attached). It uses #sorted:, so it has the same bug for SortedCollections, but I think folds might find it useful. Here are some examples:

 

 #(-14 3 1 -3 7 12) sortBy: #abs
 #(-14 3 1 -3 7 12) sortBy: #(abs yourself)
 #(-14 3 1 -3 7 12) sortBy: [:x | x \\ 4]
 #(-14 3 1 -3 7 12) sortBy: (List with: [:x | x \\ 4] with: #yourself)

 

The default sort order is ascending, but a variant allows a descending sort:

 

 aCollection sortBy: #name ascending: false

 

I don't like that #sortBy: seems to imply a mutation of the receiver while actually providing a new collection. Perhaps I should have named it #sortedBy: or something. Handling the arguments:
 ...
 value1 := unarySelectorOrBlock isSymbol
  ifTrue: [element1 perform: unarySelectorOrBlock]
  ifFalse: [unarySelectorOrBlock value: element1].
 ...

 

could be streamlined a bit if Squeak Extensions are loaded (which defines Symbol>>value:):
 ...
 value1 := unarySelectorOrBlock value: element1.
 ...

 

but the attached version works in vanilla VW 7.6. In our code, only a few percent of senders of #sortBy: pass a block (likely because #sorted: and #asSortedCollection: already take a block). About a quarter of our senders pass a collection of selectors, and the rest pass a single selector. I've not yet had a desire to pass a mixed collection containing blocks and selectors, but the examples in the method comments validate that case.

 

Paul indicated that #asSortedCollection: is faster than #sorted:, so if that is important to you I confess I did not optimize #sortBy: for speed.

 

If Cincom felt so inclined, they could probably modify #sorted: to take a block, a selector, or a collection thereof, making that single api more flexible, and eliminating my desire for a separate #sortBy: api. Or, the attached can be freely used/modified by anyone.

 

Dave Stevenson
[hidden email]

 

 

---

From: Paul Baumann [hidden email]
To: Julian Fitzell [hidden email]; "Joerg Beekmann, DeepCove Labs (YVR)" [hidden email]; [hidden email] [hidden email]
Sent: Mon, August 9, 2010 12:32:58 PM
Subject: Re: [vwnc] Surprise of the day


>> I think it would read "Answer a sequenceable collection containing the contents of the receiver sorted according to aBlock. The receiver is not modified."

Yes, that is a better method comment.

#sorted: is broken, uncommented (at least as of VW 7.5), typically slower, and non-portable. You think #sorted: can be better than #asSortedCollection: and should be fixed instead of removed, I respect that. I see why you appreciate it. I'll stick with #asSortedCollection: until #sorted: is better.

Paul Baumann


-----Original Message-----
From: Julian Fitzell [mailto:[hidden email]]
Sent: Monday, August 09, 2010 6:03 AM
To: Paul Baumann; 'Joerg Beekmann, DeepCove Labs (YVR)'; [hidden email]
Subject: Re: [vwnc] Surprise of the day
Importance: High

On 10-08-06 4:58 PM, "Paul Baumann" <[hidden email]> wrote:
> If the purpose of #sorted: were documented, I think it would read
> "Answer a collection similar to the receiver with contents sorted according to aBlock".
> The "similar to the receiver" part is the only part that would
> distinguish it from #asSortedCollection:.

I disagree. I think it would read "Answer a sequenceable collection containing the contents of the receiver sorted according to aBlock. The receiver is not modified."

A SortedCollection is specifically implemented to allow the contents to change and to remain sorted when elements are added. If you don't need that functionality, there's no point demanding a SortedCollection. #sorted:
allows each collection to make the decision of how to most efficiently create and return the result, whether that is returning a copy of self, a copy with the sort block changed, an Array created in some fashion or other, or some other method. It's a protocol that allows you ask for something specific that you need without specifying the implementation, which is exactly what OO is supposed to be about.

Julian



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>> I think it would read "Answer a sequenceable collection containing the contents of the receiver sorted according to aBlock. The receiver is not modified."

Yes, that is a better method comment.

#sorted: is broken, uncommented (at least as of VW 7.5), typically slower, and non-portable. You think #sorted: can be better than #asSortedCollection: and should be fixed instead of removed, I respect that. I see why you appreciate it. I'll stick with #asSortedCollection: until #sorted: is better.

Paul Baumann


-----Original Message-----
From: Julian Fitzell [[hidden email]]
Sent: Monday, August 09, 2010 6:03 AM
To: Paul Baumann; 'Joerg Beekmann, DeepCove Labs (YVR)'; [hidden email]
Subject: Re: [vwnc] Surprise of the day
Importance: High

On 10-08-06 4:58 PM, "Paul Baumann" <[hidden email]> wrote:
> If the purpose of #sorted: were documented, I think it would read
> "Answer a collection similar to the receiver with contents sorted according to aBlock".
> The "similar to the receiver" part is the only part that would
> distinguish it from #asSortedCollection:.

I disagree. I think it would read "Answer a sequenceable collection containing the contents of the receiver sorted according to aBlock. The receiver is not modified."

A SortedCollection is specifically implemented to allow the contents to change and to remain sorted when elements are added. If you don't need that functionality, there's no point demanding a SortedCollection. #sorted:
allows each collection to make the decision of how to most efficiently create and return the result, whether that is returning a copy of self, a copy with the sort block changed, an Array created in some fashion or other, or some other method. It's a protocol that allows you ask for something specific that you need without specifying the implementation, which is exactly what OO is supposed to be about.

Julian



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>> I think it would read "Answer a sequenceable collection containing the contents of the receiver sorted according to aBlock. The receiver is not modified."

Yes, that is a better method comment.

#sorted: is broken, uncommented (at least as of VW 7.5), typically slower, and non-portable. You think #sorted: can be better than #asSortedCollection: and should be fixed instead of removed, I respect that. I see why you appreciate it. I'll stick with #asSortedCollection: until #sorted: is better.

Paul Baumann


-----Original Message-----
From: Julian Fitzell [[hidden email]]
Sent: Monday, August 09, 2010 6:03 AM
To: Paul Baumann; 'Joerg Beekmann, DeepCove Labs (YVR)'; [hidden email]
Subject: Re: [vwnc] Surprise of the day
Importance: High

On 10-08-06 4:58 PM, "Paul Baumann" <[hidden email]> wrote:
> If the purpose of #sorted: were documented, I think it would read
> "Answer a collection similar to the receiver with contents sorted according to aBlock".
> The "similar to the receiver" part is the only part that would
> distinguish it from #asSortedCollection:.

I disagree. I think it would read "Answer a sequenceable collection containing the contents of the receiver sorted according to aBlock. The receiver is not modified."

A SortedCollection is specifically implemented to allow the contents to change and to remain sorted when elements are added. If you don't need that functionality, there's no point demanding a SortedCollection. #sorted:
allows each collection to make the decision of how to most efficiently create and return the result, whether that is returning a copy of self, a copy with the sort block changed, an Array created in some fashion or other, or some other method. It's a protocol that allows you ask for something specific that you need without specifying the implementation, which is exactly what OO is supposed to be about.

Julian



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>> they are likely to do almost exactly the same work
 
Creating a copy of a hashed collection is less efficient than enumerating a hashed collection to copy elements into an array. The difference is in the hidden cost of hashing for the copy. Compare performance yourself. I gave examples.

>>'aCollection asSortedCollection asArray' which makes two copies of the collection
 
Yes. That is the only reason why #sorted: was 5% faster in one example. Consider though, that if a SortedCollection is a reasonable response type then skip the #asArray conversion and get the fastest of all options.

>>The method [#sorted:] doesn't work for some collections...That doesn't seem like a huge limitation.
 
It caused problems for us as code evolved. Other collection types came into use. Errors were discovered late in the release cycle. That is the primary reason why all code had been changed to avoid sending #sorted:.
 
>> The SequenceableCollection>>sorted: method is commented in current versions.
 
Good, probably from the last time this topic came up. That is why I mentioned that I'm using VW 7.5. I don't know what it looks like in VW 7.7.
 
>> It's not portable, although it is also in some other dialects. If you wish to write strictly portable code, then it's a construct to be avoided.
 
So in which dialects does it behave similarly? Does it error there also? If there had been any performance advantage to using #sorted: then it would have been kept despite the code not being portable--presuming errors were fixed too.

 
Paul Baumann
 
 
 

---

From: Alan Knight [[hidden email]]
Sent: Tuesday, August 10, 2010 10:16 AM
To: Paul Baumann; 'Julian Fitzell'; 'Joerg Beekmann, DeepCove Labs (YVR)'; [hidden email]
Subject: Re: [vwnc] Surprise of the day
Importance: High

I have trouble seeing why #sorted: would be in general slower than asSortedCollection, as they are likely to do almost exactly the same work. I don't think that SequenceableCollectionSorter is radically less efficient than the algorithm encoded into SortedCollection, and if it is, that's something that should be fixed. I particularly have trouble seeing that the usage this would be most useful for, replacing
   aCollection asSortedCollection asArray
which makes two copies of the collection (unless it's already a SortedCollection) would in general run faster than making one copy via
  aCollection sorted

The method doesn't work for some types of collections, specifically anything that a SequenceableCollectionSorter won't work on, and which implement one of the methods involved specifically. That doesn't seem like a huge limitation, and it's one that's pretty easily fixed, as discussed in this thread.

The SequenceableCollection>>sorted: method is commented in current versions.

It's not portable, although it is also in some other dialects. If you wish to write strictly portable code, then it's a construct to be avoided.

At 03:32 PM 2010-08-09, Paul Baumann wrote:

>> I think it would read "Answer a sequenceable collection containing the contents of the receiver sorted according to aBlock. The receiver is not modified."

Yes, that is a better method comment.

#sorted: is broken, uncommented (at least as of VW 7.5), typically slower, and non-portable. You think #sorted: can be better than #asSortedCollection: and should be fixed instead of removed, I respect that. I see why you appreciate it. I'll stick with #asSortedCollection: until #sorted: is better.

Paul Baumann


-----Original Message-----
From: Julian Fitzell [ [hidden email]]
Sent: Monday, August 09, 2010 6:03 AM
To: Paul Baumann; 'Joerg Beekmann, DeepCove Labs (YVR)'; [hidden email]
Subject: Re: [vwnc] Surprise of the day
Importance: High

On 10-08-06 4:58 PM, "Paul Baumann" <[hidden email]> wrote:
> If the purpose of #sorted: were documented, I think it would read
> "Answer a collection similar to the receiver with contents sorted according to aBlock".
> The "similar to the receiver" part is the only part that would
> distinguish it from #asSortedCollection:.

I disagree. I think it would read "Answer a sequenceable collection containing the contents of the receiver sorted according to aBlock. The receiver is not modified."

A SortedCollection is specifically implemented to allow the contents to change and to remain sorted when elements are added. If you don't need that functionality, there's no point demanding a SortedCollection. #sorted:
allows each collection to make the decision of how to most efficiently create and return the result, whether that is returning a copy of self, a copy with the sort block changed, an Array created in some fashion or other, or some other method. It's a protocol that allows you ask for something specific that you need without specifying the implementation, which is exactly what OO is supposed to be about.

Julian



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>> they are likely to do almost exactly the same work
 
Creating a copy of a hashed collection is less efficient than enumerating a hashed collection to copy elements into an array. The difference is in the hidden cost of hashing for the copy. Compare performance yourself. I gave examples.

>>'aCollection asSortedCollection asArray' which makes two copies of the collection
 
Yes. That is the only reason why #sorted: was 5% faster in one example. Consider though, that if a SortedCollection is a reasonable response type then skip the #asArray conversion and get the fastest of all options.

>>The method [#sorted:] doesn't work for some collections...That doesn't seem like a huge limitation.
 
It caused problems for us as code evolved. Other collection types came into use. Errors were discovered late in the release cycle. That is the primary reason why all code had been changed to avoid sending #sorted:.
 
>> The SequenceableCollection>>sorted: method is commented in current versions.
 
Good, probably from the last time this topic came up. That is why I mentioned that I'm using VW 7.5. I don't know what it looks like in VW 7.7.
 
>> It's not portable, although it is also in some other dialects. If you wish to write strictly portable code, then it's a construct to be avoided.
 
So in which dialects does it behave similarly? Does it error there also? If there had been any performance advantage to using #sorted: then it would have been kept despite the code not being portable--presuming errors were fixed too.

Paul Baumann
 
 
 

---

From: Alan Knight [[hidden email]]
Sent: Tuesday, August 10, 2010 10:16 AM
To: Paul Baumann; 'Julian Fitzell'; 'Joerg Beekmann, DeepCove Labs (YVR)'; [hidden email]
Subject: Re: [vwnc] Surprise of the day
Importance: High

I have trouble seeing why #sorted: would be in general slower than asSortedCollection, as they are likely to do almost exactly the same work. I don't think that SequenceableCollectionSorter is radically less efficient than the algorithm encoded into SortedCollection, and if it is, that's something that should be fixed. I particularly have trouble seeing that the usage this would be most useful for, replacing
   aCollection asSortedCollection asArray
which makes two copies of the collection (unless it's already a SortedCollection) would in general run faster than making one copy via
  aCollection sorted

The method doesn't work for some types of collections, specifically anything that a SequenceableCollectionSorter won't work on, and which implement one of the methods involved specifically. That doesn't seem like a huge limitation, and it's one that's pretty easily fixed, as discussed in this thread.

The SequenceableCollection>>sorted: method is commented in current versions.

It's not portable, although it is also in some other dialects. If you wish to write strictly portable code, then it's a construct to be avoided.

At 03:32 PM 2010-08-09, Paul Baumann wrote:

>> I think it would read "Answer a sequenceable collection containing the contents of the receiver sorted according to aBlock. The receiver is not modified."

Yes, that is a better method comment.

#sorted: is broken, uncommented (at least as of VW 7.5), typically slower, and non-portable. You think #sorted: can be better than #asSortedCollection: and should be fixed instead of removed, I respect that. I see why you appreciate it. I'll stick with #asSortedCollection: until #sorted: is better.

Paul Baumann


-----Original Message-----
From: Julian Fitzell [ [hidden email]]
Sent: Monday, August 09, 2010 6:03 AM
To: Paul Baumann; 'Joerg Beekmann, DeepCove Labs (YVR)'; [hidden email]
Subject: Re: [vwnc] Surprise of the day
Importance: High

On 10-08-06 4:58 PM, "Paul Baumann" <[hidden email]> wrote:
> If the purpose of #sorted: were documented, I think it would read
> "Answer a collection similar to the receiver with contents sorted according to aBlock".
> The "similar to the receiver" part is the only part that would
> distinguish it from #asSortedCollection:.

I disagree. I think it would read "Answer a sequenceable collection containing the contents of the receiver sorted according to aBlock. The receiver is not modified."

A SortedCollection is specifically implemented to allow the contents to change and to remain sorted when elements are added. If you don't need that functionality, there's no point demanding a SortedCollection. #sorted:
allows each collection to make the decision of how to most efficiently create and return the result, whether that is returning a copy of self, a copy with the sort block changed, an Array created in some fashion or other, or some other method. It's a protocol that allows you ask for something specific that you need without specifying the implementation, which is exactly what OO is supposed to be about.

Julian



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