This cropped up in Dolphin some years back. IIRC, OA's answer was that streams historically worked on only Array and maybe something else. Having said that, they relaxed a constraint because it was harmless and a good idea. I'm not sure about streaming over a set; lack of order means that it might be tricky to maintain a reasonable position?? ________________________________________ From: pharo-project-bounces@lists.gforge.inria.fr [pharo-project-bounces@lists.gforge.inria.fr] On Behalf Of Stéphane Ducasse [stephane.ducasse@inria.fr] Sent: Tuesday, August 24, 2010 7:18 AM To: Pharo-project@lists.gforge.inria.fr Subject: Re: [Pharo-project] Why is readStream on SequenceableCollection and not on Collection? did you try with nile? because I forgot (of course doing too many things) but the difference between squeak and VW was that we could not have a stream on something else than string and array. Now this may have changed in squeak with the work of levente or nicolas. Stef On Aug 24, 2010, at 1:11 PM, Bart Gauquie wrote:

Dear list,

is there a specific reason readStream is defined on SequenceableCollection and not on Collection?

I want to for instance stream over a Set (in a non determined order).

I tried to do readStream on a Set, but got an error that copyFrom:to: was not defined on Set; so:

ReadStream>>on: aCollection

I think should read:

ReadStream>>on: aSequenceableCollection

Or should I always use: collect: select: detect: protocols?

Any thoughts on this?

Kind Regards

Bart

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Den 24.08.2010 17:58, skrev Nicolas Cellier:

2010/8/24 Schwab,Wilhelm K <bschwab@anest.ufl.edu>:

...

This cropped up in Dolphin some years back. IIRC, OA's answer was that streams historically worked on only Array and maybe something else. Having said that, they relaxed a constraint because it was harmless and a good idea.

I'm not sure about streaming over a set; lack of order means that it might be tricky to maintain a reasonable position??

Exactly, the Stream would hardly be positionable, unless you use a sort of OrderedSet... A ReadWriteStream would be problematic for the same reasons.

What would be the interest of such a Stream ? (I mean something more than what just you can do with #do:or #add:)

Nicolas +1. I don't quite see what use could would find in a stream of a non-sequenced source that is not better served by using a different abstraction, or the source itself..

Cheers, Henry

Den 25.08.2010 12:58, skrev Bart Gauquie:

On Wed, Aug 25, 2010 at 10:38 AM, Henrik Johansen <henrik.s.johansen@veloxit.no <mailto:henrik.s.johansen@veloxit.no>> wrote:

Den 24.08.2010 17:58, skrev Nicolas Cellier: > 2010/8/24 Schwab,Wilhelm K <bschwab@anest.ufl.edu <mailto:bschwab@anest.ufl.edu>>: > >> This cropped up in Dolphin some years back. IIRC, OA's answer was that streams historically worked on only Array and maybe something else. Having said that, they relaxed a constraint because it was harmless and a good idea. >> >> I'm not sure about streaming over a set; lack of order means that it might be tricky to maintain a reasonable position?? >> >> > Exactly, the Stream would hardly be positionable, unless you use a > sort of OrderedSet... > A ReadWriteStream would be problematic for the same reasons. > > What would be the interest of such a Stream ? > (I mean something more than what just you can do with #do:or #add:) > > Nicolas +1. I don't quite see what use could would find in a stream of a non-sequenced source that is not better served by using a different abstraction, or the source itself..

Cheers, Henry

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Ok, but why can you then do a collect:[] / select:[] / do: [] over a set? It also iterates over all the elements. So why is it then strange to have a readstream over a set? I'm not saying it should be a positionable stream.

But I also agree that is more logical to only do a ReadStream over a SequenceableCollection if you take into account positions ... Maybe change the code so that it only accepts a SequenceableCollection?

Haven't tried Nile yet.

Kind Regards,

Bart

Yes they iterate of the elements, but they don't really care about which. sequence the elements are in. Sure you can write a block to pass to them which does, but I doubt you'd want to use that with a Set or a Dictionary. #next, #nextPut:, #upTo: and the rest of the Stream protocol certainly do care what sequence the elements are in. Cheers, Henry