Beginners November 2013

beginners@lists.squeakfoundation.org

8 participants
9 discussions

sub-optimal optimizations
by paolo.bernardi.67＠gmail.com 27 Nov '13

27 Nov '13

ok: 1+1 can be optimized, but all objects in the universe that are not numbers are different. Nicolas: what should respond: ^'6:30am' asTime class allInstances size in the scenario of my crazy-optimization? I guess: tons of Time's, including the freezed one (6:30). But the freezed-6:30 is always the same? Yes, otherwise it means #asTime is always-evaluated. ...not too far from pre-calculating all cos and sin values of 360 degrees and storing in two arrays of 360 elements. Anyway I see it's a bad way...

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a policies system
by paolo.bernardi.67＠gmail.com 26 Nov '13

26 Nov '13

my annoyng tennis club need to implement some logics about how/when/wether a user can request/obtain the reservation of a tennis playground. I'm persuaded that smalltalk should not hard-code domain specific rules, instead: domain-neutral objects should be used/combined to reify domain objects. In this way the modification of business rules falls in the user space. So I'm thinking about Resource / Activity and Policy + Rule objects. Resource should render the concept of "things a user can deal with", Activity what "a user can do with resources". Policy/Rule should implement tools to combine them into logics that control and command resources and activities. Strategy is the design pattern I know as nearest to what I'm thinking, but it's still too restricted as scope. I don't figure where (...I'm sure is around...) in Squeak/Pharo does exist something like my "policies". tnx

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a Timetable
by paolo.bernardi.67＠gmail.com 26 Nov '13

26 Nov '13

I'm trying to realize a system that helps on booking the reservations requests of tennis plygrounds in a tennis club. Every club has its not-so-simple opening timetable. I want to let user building timetables of any complexity degree, say: with a lot of rules. So I start handling blocks like: [ :time | time asTime >= '8:30 am' asTime] thinking that they will be called many many times, and many many times will be performed the same parsing of the same string '8:30'. The way I'm following is using TimeRule objects instead of "raw" BlockCLosures. TimeRule evaluates the "asTime" value and caches it for late re-use. At the end the "optimization" meant creating specialized objects. Does anyone know about a library that implements time ranges? Not as Duration's, that occurs at a given time, but ranges that apply to any time (i.e. from January to June from 8:30 am to 5 pm but from June to December from 9 am to 10 pm).

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[ot] how to quote? :-)
by paolo.bernardi.67＠gmail.com 26 Nov '13

26 Nov '13

maybe internet changed. In the past I used to add a greater-than to the left of some rows of text. It was a quote. Now I send commands to the list (luckly left unprocessed!)

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Re: optimization (2nd attempt)
by paolo.bernardi.67＠gmail.com 25 Nov '13

25 Nov '13

Sorry, I'm not so smart when quoting... Il 24/11/2013 15.39, Levente Uzonyi wrote: > Since message sends are late bound, it means that if you want to cache > something, then you have to do it yourself. I know (or I think I know) what late binding means, but I can't figure the connection with the topic of caching the return value. In other words: if st was NOT late binding, things were different about the to cache or not to cache some return value? Can you clear to me the idea? molte grazie (= many thanks)

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Re: optimization (and late binding)
by paolo.bernardi.67＠gmail.com 25 Nov '13

25 Nov '13

Thanks, I realized that it's not such true that a message sent to a constant value *must* return a constant value too. Il 24/11/2013 15.39, Levente Uzonyi ha scritto: > Since message sends are late bound, it means that if you want to cache > something, then you have to do it yourself. I know (or I think I know) what late binding means, but I can't figure the connection with the topic of caching the return value. In other words: if st was NOT late binding, things were different about the to cache or not to cache some return value? Can you clear to me the idea? molte grazie (= many thanks)

1 0

optimization
by paolo.bernardi.67＠gmail.com 24 Nov '13

24 Nov '13

hi all, expressions based on constants are remembered/cached for next evalations? If I compile: Foo>>wakeUpTime ^ '6:30 am' asTime I can see that bytecode still send #asTime to the string '6:30 am'. It means that each time the piece of code will be evaluated the string will be parsed too, even if it is clear that it will never produce a different object. Same thing for CodeBlocks. In: [ :t | t < '06:30' asTime ] the right argument of #> will never change... and I feel I'll spend a lot of time on evaluating the same constant expressions during the execution of my program... thanks Paolo

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Subclasses in Squeak
by Azka Niazi 21 Nov '13

21 Nov '13

What is the significance of using methods given below for the class classBuilder, which in effect are used for creating subclasses of these different categories? Meaning, is there something dramatic about making these different types of subclasses instead of just simply having something like a generic subclass only? superclass: t1 subclass: t2 instanceVariableNames: t3 classVariableNames: t4 poolDictionaries: t5 category: t6 superclass: t1 variableByteSubclass: t2 instanceVariableNames: t3 classVariableNames: t4 poolDictionaries: t5 category: t6 superclass: t1 variableSubclass: t2 instanceVariableNames: t3 classVariableNames: t4 poolDictionaries: t5 category: t6 superclass: t1 variableWordSubclass: t2 instanceVariableNames: t3 classVariableNames: t4 poolDictionaries: t5 category: t6 superclass: t1 weakSubclass: t2 instanceVariableNames: t3 classVariableNames: t4 poolDictionaries: t5 category: t6

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Is Squeak/Pharo an appropriate language choice?
by Charles Hixson 02 Nov '13

02 Nov '13

I'm contemplating a project that would benefit greatly by a persistent memory image, though I'll eventually (in a year or so) need the 64-bit image, but: The image will be a lot larger than RAM. It would include a directed graph that had an index of a million or so entries, and most nodes wouldn't be indexed. So in order to even load it would need to use some sort of lazy access. And I'm not even sure that a Dictionary of over a million items is reasonable. (Naturally none of the examples address this problem.) Additionally, all of my (written) documentation is so old that it doesn't even discuss multi-processor systems, so I don't know whether modern Smalltalks make any use of additional available processors. I'd really like some advice, and possibly some references. I know that Smalltalk has the reputation for being slow (yes, I've been reading about the recent speed-ups), but much of what I'd need to write in any other language seems like it may already be present in Smalltalk, so if it would work, I'd like to choose it. But I won't be able to test this until the application has been running for quite awhile, so I would be very desirable that I know ahead of time. -- Charles Hixson

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Beginners November 2013