May 2011 - Pharo-dev - lists.pharo.org

[Pharo-project] Set with nil
by Guillermo Polito May 21, 2011

May 21, 2011

Hi! Since a year ago, we have this issue: http://code.google.com/p/pharo/issues/detail?id=1907 There were 2 solutions proposed, and the 2 were developed by different people. But for some reason it was not integrated and continuously postponed. So, my question is: Do we want Sets accepting nil? If we don't, the issue is invalid. If we do, can someone review the code proposed? Thanks! Guille

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[Pharo-project] VW's ObjectRegistry similar in Pharo?
by Mariano Martinez Peck May 21, 2011

May 21, 2011

Hi guys. We are doing graph traversal (for Fuel) and we would love a collection to be really fast and only support two simple operations: #add: and #includes: The idea is that each object we process of the graph we put it in the collection and then for each object we have to ask whether it is included or not (to avoid cycles and putting the same object more than once). VW seems to have ObjectRegistry (subclass of IdentitySet) which is more or less that. It is used by ObjectTracer, which in fact is what we want to do. And even more, Parcels uses that ;) (or an extension of that). So...I wonder, is there a special collection implementation ideal for this case? is something similar to ObjectRegistry available for pharo ? Thanks in advance, -- Mariano http://marianopeck.wordpress.com

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[Pharo-project] [Hudson] Jenkins
by Marcus Denker May 21, 2011

May 21, 2011

Yes! https://ci.lille.inria.fr/pharo/ All existing accounts should work, but it is empty right now. We will test it a bit and then think about how to move all configs there. This setup has the possibility of defining a "staging" project. This is run as soon as an updated jenkins is available and on green --> the whole installation updates to the latest jenkins automaticaly. Marcus -- Marcus Denker -- http://www.marcusdenker.de INRIA Lille -- Nord Europe. Team RMoD.

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Re: [Pharo-project] [squeak-dev] My solution to handling errors in system-critical processes
by Igor Stasenko May 21, 2011

May 21, 2011

On 20 May 2011 19:33, Eliot Miranda <eliot.miranda(a)gmail.com> wrote: > Hi Igor, > Â Â Â I get the idea but I does one really need on:fork: ? Â Why not add > Exception>fork, a la Exception>pass? Â So one writes > [ self doSomething Â ] on: Error do: [:ex | ex fork ]. > and if you want to specify a handler function you pass in a block: > > [ self doSomething Â ] on: Error do: [:ex | ex fork: [block to handle error > in another process here] ]. Good question. You can implement it anywhere. Except then how to correctly determine stack slicing point? Exception>>fork: aBlock contextToSlice := thisContext sender home ? see, the above is too fragile. Where the guarantees that you sending #fork: inside a block, but not like: Error new fork: [ .... ] ? If you looked at implementation, i capturing the context of a method before sending #on:do: in this way, i know the stack slicing point beforehand. But if i place it into exception, then correct behavior will have to rely on developer's sanity that he using it as intended by design. So, why putting pitfalls when we can avoid them? My choice for stack slicing point was to let user to see the closure context with on:do: while debugging, otherwise it will be harder to determine the origin of code, which led to error. Right now, if you evaluate [ 1/0 ] on: Error fork:[ :ex | ex pass ] in debugger, you will see the 2nd bottom context will be an on:do: method, and next one will contain the context for closure that is receiver of #on:do: so in this way you can clearly see the method with exception handler, who wanted to handle errors in forked process. > ? > Further, re the finalization issue why are you so resistant to the > tried-and-tested VW solution that's been in use for about a decade? i am not resistant at all. I had no time to do that. Actually, i came to this idea when looking at Henrik's code for Announcements.. and then i found that it can serve for both finalization and Announcements (and lot of other critical places, where you don't want to be killed by errors). For instance , today i shown to Stef, that by placing it at single point in WorldState>>doOneCycleNowFor: aWorld we could avoid respawning UI process each time you open debugger. You slicing the stack with error, putting it into forked process, where you can do anything with it, while UI process continues to run from known safe point. So it solves more problems than just in finalization. Also i think that it is more efficient: you pay the high price only when it is necessary - when exception happens, but if things go as expected , the overhead is minimal. While in solution which you describing, the price was higher, since you have to pass the finalizer to forked process and signal semaphore, and then wait till it finish or fork another process. And synchronization is not cheap, and moreover, you will have 1 extra process hanging around all the time. While now i can simply do: executors do: [:executor | [ executor finalize ] on: Exception fork: [ :ex | ex pass ] ] > best, > Eliot -- Best regards, Igor Stasenko AKA sig.

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[Pharo-project] The Cult of Done Manifesto
by Marcus Denker May 21, 2011

May 21, 2011

The Cult of Done Manifesto - There are three states of being. Not knowing, action and completion. - Accept that everything is a draft. It helps to get it done. - There is no editing stage. - Pretending you know what you're doing is almost the same as knowing what you are doing, so just accept that you know what you're doing even if you don't and do it. - Banish procrastination. If you wait more than a week to get an idea done, abandon it. - The point of being done is not to finish but to get other things done. - Once you're done you can throw it away. - Laugh at perfection. It's boring and keeps you from being done. - People without dirty hands are wrong. Doing something makes you right. - Failure counts as done. So do mistakes. - Destruction is a variant of done. - If you have an idea and publish it on the internet, that counts as a ghost of done. - Done is the engine of more. http://www.brepettis.com/blog/2009/3/3/the-cult-of-done-manifesto.html?v=1 -- Marcus Denker -- http://www.marcusdenker.de INRIA Lille -- Nord Europe. Team RMoD.

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[Pharo-project] SerialPort Plugin Patches.
by Friedrich Dominicus May 21, 2011

May 21, 2011

I've downloaded the Cog sources and checked the SerialPlugin stuff. I'd like to use it with the patches that will make it work on Linux also but for that there should be a primite with printPortByName or the like, but it's not in the actual sources. So can anyone tell me where an actualiced SerialPlugin is, with which I then can use strings for accessing the serial lines? Thanks Friedrich -- Q-Software Solutions GmbH; Sitz: Bruchsal; Registergericht: Mannheim Registriernummer: HRB232138; Geschaeftsfuehrer: Friedrich Dominicus

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[Pharo-project] Can't load OSProcess in last Pharo Core 1.3
by Adrien BARREAU May 20, 2011

May 20, 2011

Hi all, I just tried to load OSProcess in the last PharoCore 1.3 (I took it from hudson). It fails when it tries to add ThisOSProcess to the startup list with: Smalltalk addToStartUpList: ThisOSProcess after: ImageSegment. in ThisOSProcess class>>initialize. It seems that ImageSegment is not in the StartUpList anymore. Is that normal? Adrien.

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[Pharo-project] suppressing the ob ast navigation
by Tudor Girba May 20, 2011

May 20, 2011

Hi, In the latest OB, pressing ctrl+shift+(left/right)arrow gets you to navigate through the AST. This is certainly cool, but I could not find a usage for it yet :). But, the problem is that it overloads the ctrl+shift which in any text editor selects the previous/next word. If this feature is indeed wanted, could we find another keybinding solution for it? If not, how can I disable it in my image? Cheers, Doru -- www.tudorgirba.com "Presenting is storytelling."

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Re: [Pharo-project] Name spaces
by Marcus Denker May 20, 2011

May 20, 2011

On May 20, 2011, at 3:43 PM, Philippe Marschall wrote: > On 05/20/2011 02:52 PM, Janko MivÅ¡ek wrote: >> On 20. 05. 2011 14:15, StÃ©phane Ducasse wrote: >> >>>>>> I'm wondering what is the status of the name spaces project developed last summer as part of GSoC. >>>>> >>>>> nowhere and do not expect it to be in pharo. >>>> >>>> Why that? Is it because of the implementation or because you don't want >>>> namespaces in Pharo? >>> >>> sorry guy I do not have the time for discussing that. >> >> But it is certainly needed to be discussed and it would be nice if at >> least a timeframe for this discussion is announced. If not put in a plan >> for Pharo ... > > Yes, name spaces haven't yet been discussed enough. > Maybe we can establish a new tradition and have a 100+ discussion about namespaces every year. It worked well for Squeak... Marcus -- Marcus Denker -- http://www.marcusdenker.de INRIA Lille -- Nord Europe. Team RMoD.

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[Pharo-project] My solution to handling errors in system-critical processes
by Igor Stasenko May 20, 2011

May 20, 2011

Hello, if you remember , there was a discussion about how to solve efficiently a following problem: We have a critical processes running in system, which usually running an infinite loop and providing some service(s), which triggered periodically. A most common case is weak finalization. We need to ensure that finalization works, and if finalization of some object causing an error, it should not affect the finalization of the rest of object(s) nor affect the finalization process (like suspending it or terminating it). Also, in another discussion about Announcements, we found that same requirement actually should be fulfilled by Announcement framework: a delivery of a single announcement to some subscriber may fail, however regardless of such failure, other subscribers should be able to receive an announcement no matter what happen. There was a different solutions proposed, like finalizing a single object in separate, forked process, so even if it will fail with error, the rest of finalizers are not affected by this and finalization process continues to run normally. However its not very effective, because you paying the cost of forking process each time you need to finalize new object. There was an optimized solution, but nevertheless it doesn't changing the idea: perform a single item finalization in separate process. Another (a bit lame) approach is to simply swallow any errors, and while it provides guarantee that your critical process won't be terminated due to errors, at the same time, it makes impossible to detect and fix error(s), which of course should be taken care of to prevent them from appearing in future. So, my idea is to fork only if error happens. Add a new protocol to BlockClosure, which could allow us to handle errors in special manner: [ self doSomething ] on: Error fork: [:ex | handle error here ]. it is similar to #on:do: , except that in case of error, and error handler is invoked in separate forked process, while original process simply returns from closure activation with nil return value. But don't think that it is implemented as simple as: on: error fork: handleAction ^ self on: error do: [:ex | [handleAction cull: ex ] fork ]. it would be too easy and therefore useless. :) Because when you do it like that, a debugger window which opens an error, will not show you the stack contents which you wanna see. And then you will have to manually inspect the exception and then inspect an exception context and so on, in order to determine what caused error. What my implementation does, is actually splits the stack of current process and all contexts which are above #on:fork: method is going to forked process, while original process simply returns to sender of #on:fork: with nil return value. So, consider the original stack of a single process: a. <bottom> a. ... a. ... sender of #on:fork: b. <#on:fork:> b. #on:do: b. ... b. ... b. ... b. SomeError signal. b. ... b. ... b. error handler. then in case of exception, all contexts labeled by (a) are left in original process, and original process continues execution from sender of on:fork:, while contexts labeled by (b) is transferred to a newly forked process. In this way, if exception is unhandled (if you put 'ex pass' there), the debugger will show a usual stack trace, as you normally see when error occurs, except that you don't see stack below #on:do: method (which is a context next to #on:fork:), but that's already enough information to determine what causing an error and even fix it and complete the action! So, we can have a cake (a fault-tolerant critical services) and eat it too (conveniently debug errors which could happen there), and without extra overhead. Please review my implementation. I tried it with could different exceptions and it works fine. However there could be some caveats. I tried it on Cog and it works fine. If there everything ok, then we can start using this method in finalization and in announcements, which will improve our systems stability and make it much easier to deal with errors there :) -- Best regards, Igor Stasenko AKA sig.

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