November 2017 - Pharo-users

Re: [Pharo-users] Timespan translateToUTC problematic
by Sean P. DeNigris Nov. 22, 2017

Nov. 22, 2017

Pharo Smalltalk Users mailing list wrote > #hasSameDayAs:Â ----------------- Wouldn't that be #isSameDayAs:? ----- Cheers, Sean -- Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html

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About implementing a "Mini Pillar" in-image renderer for Pharo ...
by H. Hirzel Nov. 21, 2017

Nov. 21, 2017

Hello In the thread 'including Pillar in Pharo image by default' it was suggested by Stephane Ducasse to include a subset of Pillar in the Pharo image[1] . I'd like to extend that proposal a little bit it in order to do very simple presentations. This should allow to describe at least part of the slides used in the MOOC course [3]. This will be _a possible_ solution to the question brought up in the thread 'Writing "powerpoint" like presentations in Pharo?'. Another use is to write instructions with executable content within the image ("Assistants"). So below is the a proposal for a Pillar syntax _subset_ for class comments and _simple_ presentations. The numbering scheme follows the 'Pillar syntax cheat sheet' [2] MINI PILLAR SYNTAX (a subset of Pillar) 1. Headers !Header 1 !!Header 2 !!!Header 3 2. Lists - Unordered List # Ordered list 5. Emphasis ""bold"" 6. Code blocks [[[ Transcript show: 'Hello World'. \]]] 9. Annotation ${slide:title=About Pharo}$ Next week I plan to implement the rendering of this 'Mini Pillar' in Morphic using the Morphic API subset that works in Pharo and Squeak. A renderer using Bloc would also be nice. [4] Comments, suggestions, code snippets and other help is welcome. Regards Hannes -------------------------------------------------------------------------------------------------- [1] Pillar subset for class comments Stephane Ducasse <stepharo.self(a)gmail.com> Fri, Aug 11, 2017 at 7:09 PM To: Any question about pharo is welcome <pharo-users(a)lists.pharo.org> Tx cyril For class comment I image that we want ! - - *url* and bold [[[ ]]] Did I miss something. Stef -------------------------------------------------------------------------------------------------- [2] http://pillarhub.pharocloud.com/hub/pillarhub/pillarcheatsheet -------------------------------------------------------------------------------------------------- 1. Headers !Header 1 !!Header 2 !!!Header 3 !!!!Header 4 !!!!!Header 5 !!!!!!Header 6 2. Lists - Unordered List # Ordered list 3. Table |! Left |! Right |! Centered |{Left |}Right| Centered 4. Description Note on a new line ;head :item 5. Emphasis ""bold"" ''italic'' --strikethrough-- __underscore__ ==inline code== @@subscript@@ ^^sub-script^^ 6. Code blocks [[[labÂel=ÂhelÂloSÂcriÂpt|ÂcapÂtioÂn=How to print Hello World|ÂlanÂguaÂge=ÂSmaÂlltalk Transcript show: 'Hello World'. \]]] 7. Raw {{{latex: this is how you inject raw \LaTeX in your output file }}} {{{marÂkdown: this is how you inject raw `markdown` in your output file }}} {{{html: this is how you inject raw <b>ÂhtmÂl</Âb> in your output file }}} 8. Links Anchor @anchor (new line) Internal link *anchor* External link *Google>http://google.com* Image +Caption>file://image.png|width=50|label=label+ 9. Annotation Note on a new line Annotation @@note this is a note Todo item @@todo this is to do 10. Comments % each line starting with % is commented 11. References This document is copied from http://www.cheatography.com/benjaminvanryseghem/cheat-sheets/pillar/ ---------------------------------------------------------------------- [3] Example pillar code for slides ---------------------------------------------------------------------- https://github.com/SquareBracketAssociates/PharoMooc/blob/master/Slides/1-T… { "title":"To the Roots of Objects", "subtitle":"Learning from beauty", "author":"Stephane Ducasse", "complement":"http://stephane.ducasse.free.fr/ \\\\ stephane.ducasse(a)inria.fr" } ${toc:depthLevel=2|level=0|highlight=0}$ %Les sections ne sont pas des titres de slide mais dÃ©finnissent la structure du doucment. Il est possible de rajouter "renderStructureAsSlide":false dans pillar.conf pour ne pas crÃ©er de slide Ã partir d'un titre. ${slide:title=License}$ +>file://figures/CreativeCommons.png|width=50|label=figCreativeCommons+ ! Introduction % ${toc:depthLevel=1|level=0|highlight=1}$ ${slide:title=Really?!|label=really}$ ${columns}$ ${column:width=50}$ %the width parameter take an Int between 1 and 100 %For now we have to pass a line before and after an annotation, I'll correct that soon in Pillar. - No primitive types - No hardcoded constructs for conditional - Only messages - Only objects ${column:width=50}$ - and this works? - I mean really? - Not even slow? - Can't be real! ${endColumns}$ ${slide:title=Motto}$ - Let's open our eyes, look, understand, and deeply understand the underlying design aspects of object-oriented programming. *@really* *TEST !>@really* ${slide:title=Booleans}$ [[[language=smalltalk 3 > 0 ifTrue: ['positive'] ifFalse: ['negative'] -> 'positive' ]]] ${slide:title=Yes ifTrue\:ifFalse\: is a message!}$ [[[language=smalltalk Weather isRaining ifTrue: [self takeMyUmbrella] ifFalse: [self takeMySunglasses] ]]] - Conceptually ==ifTrue:ifFalse:== is a message sent to an object: a boolean! - ==ifTrue:ifFalse:== is in fact radically optimized by the compiler but you can implement another one such ==siAlors:sinon:== and check. ${slide:title=Booleans}$ In Pharo booleans have nothing special - & | not - or: and: (lazy) - xor: - ifTrue:ifFalse: - ifFalse:ifTrue: - ... ${slide:title=Lazy Logical Operators}$ *LINK>@frm:really* [[[language=smalltalk false and: [1 error: 'crazy'] -> false and not an error ]]] ! Exercices ${toc:depthLevel=1|level=0|highlight=1}$ !! Exercise 1: Implement not ${slide:title=Exercise 1\: Implement not}$ - Propose an implementation of not in a world where you do not have Booleans. - You only have objects and messages. [[[language=smalltalk false not -> true true not -> false ]]] !!Exercise 2: Implement | (Or) ifTrue: ifFalse: ${toc:depthLevel=2|level=0|highlight=1}$ ${slide:title=Exercise 2\: Implement \| (Or)}$ - Propose an implementation of or in a world where you do not have Booleans. - You only have objects and messages. [[[language=smalltalk true | true -> true true | false -> true true | anything -> true false | true -> true false | false -> false false | anything -> anything ]]] ${slide:title=Exercise2\: Variation - Implement ifTrue\:ifFalse\:}$ - Propose an implementation of not in a world where you do not have Booleans. - You only have objects, messages and closures. [[[language=smalltalk false ifTrue: [ 3 ] ifFalse: [ 5 ] -> 5 true ifTrue: [ 3 ] ifFalse: [ 5 ] -> 3 ]]] ! Boolean Implementation ${toc:depthLevel=1|level=0|highlight=1}$ ${slide:title=Booleans Implementation Hint One}$ - The solution does not use conditionals - else we would obtain a recursive definition of ==ifTrue:ifFalse:== ${slide:title=Boolean Implementation Hint Two}$ - The solution uses three classes: ==Boolean==, ==True== and ==False== - ==false== and ==true== are unique instances described by their own classes - ==false== is an instance of the class ==False== - ==true== is an instance of the class ==True== +Boolean Hierarchy>file://figures/BooleanHiearchyAndInstances.png|width=50+ ${slide:title=How do we express choice in OOP?}$ - We send messages to objects [[[language=smalltalk aButton color -> Color red aPane color -> Color blue aWindow color -> Color grey ]]] - Let's the receiver decide - Do not ask, tell ${slide:title=Boolean not implementation}$ - Class ==Boolean== is an abstract class that implements behavior common to true and false. Its subclasses are ==True== and ==False==. Subclasses must implement methods for logical operations ==&==, ==not==, and controls ==and:==, ==or:==, ==ifTrue:==, ==ifFalse:==, ==ifTrue:ifFalse:==, ==ifFalse:ifTrue:== [[[language=smalltalk Boolean>>not "Negation. Answer true if the receiver is false, answer false if the receiver is true." self subclassResponsibility ]]] ${slide:title=Not implementation in two methods}$ [[[language=smalltalk False>>not "Negation -- answer true since the receiver is false." ^ true ]]] [[[language=smalltalk True>>not "Negation--answer false since the receiver is true." ^ false ]]] ${slide:title=Not implementation in two methods}$ +Not implementation.>file://figures/BooleanHiearchyAndInstancesWithNotMethods.png|width=80+ ${slide:title=\| (Or)}$ [[[language=smalltalk true | true -> true true | false -> true true | anything -> true false | true -> true false | false -> false false | anything -> anything ]]] ${slide:title=Boolean>> \| aBoolean}$ [[[language=smalltalk Boolean>> | aBoolean "Evaluating disjunction (OR). Evaluate the argument. Answer true if either the receiver or the argument is true." self subclassResponsibility ]]] ${slide:title=False>> \| aBoolean}$ [[[language=smalltalk false | true -> true false | false -> false false | anything -> anything ]]] [[[language=smalltalk False >> | aBoolean "Evaluating disjunction (OR) -- answer with the argument, aBoolean." ^ aBoolean ]]] ${slide:title=True>> \| aBoolean}$ [[[language=smalltalk true | true -> true true | false -> true true | anything -> true ]]] [[[language=smalltalk True>> | aBoolean "Evaluating disjunction (OR) -- answer true since the receiver is true." ^ self ]]] ${slide:title=Or implementation in two methods}$ +>file://figures/BooleanHiearchyAndInstancesWithOrMethods.png|width=80+ ${slide:title=Implementing ifTrue\:ifFalse\:}$ - Do you see the pattern? - Remember that a closure freezes execution and that value launches the execution of a frozen code. [[[language=smalltalk True>>ifTrue: aTrueBlock ifFalse: aFalseBlock ^ aTrueBlock value ]]] [[[language=smalltalk False>>ifTrue: aTrueBlock ifFalse: aFalseBlock ^ aFalseBlock value ]]] ${slide:title=Implementation Note}$ - Note that the Virtual Machine shortcuts calls to boolean such as condition for speed reason. - But you can implement your own conditional method and debug to see that sending a message is dispatching to the right object. ! So what ? ${toc:depthLevel=1|level=0|highlight=1}$ ${slide:title=Ok so what?}$ - You will probably not implement another Boolean classes - So is it really that totally useless? ${slide:title=Message sends act as case statements}$ - The execution engine will select the right method in the class of the receiver - The case statements is dynamic in the sense that it depends on the classes loaded and the objects to which the message is sent. - Each time you send a message, the system will select the method corresponding to the receiver. ${slide:title=A Class Hierarchy is a Skeleton for Dynamic Dispatch}$ - If we would have said that the ==Boolean== would be composed of only one class, we could not have use dynamic binding. - A class hierarchy is the exoskeleton for dynamic binding - Compare the solution with one class vs. a hierarchy. +One single class vs. a nice hierarchy.>file://figures/Design-FatVsDispatch.png|width=70+ - The hierarchy provides a way to specialize behavior. - It is also more declarative in the sense that you only focus on one class. - It is more modular in the sense that you can package different classes in different packages. ${slide:title=Avoid Conditionals}$ - Use objects and messages, when you can - The execution engine acts as a conditional switch: Use it! - Check the AntiIfCampaign. ${slide:title=Follow-up: Implement ternary logic}$ - Boolean: ==true==, ==false==, ==unknown== +Ternaru Logic decision table >file://figures/ArrayBoolean.png|width=30|label=fig:ternLogic+ - Implementing in your own classes. ! Summary ${toc:depthLevel=1|level=0|highlight=1}$ ${slide:title=Summary}$ - Tell, do not ask - Let the receiver decide - Message sends as potential dynamic conditional - Class hiearchy builds a skeleton for dynamic dispatch - Avoid conditional ----------------------------------------- [4] Bloc Load Bloc with executing in a playground (Pharo 6.1) Metacello new baseline: 'Bloc'; repository: 'github://pharo-graphics/Bloc:pharo6.1/src'; load: #core A tutorial to use bloc is available on http://files.pharo.org/books/ Bloc Memory Game (alpha) is a first tutorial on Bloc the new graphics core for Pharo. Booklet written by A. Chis, S. Ducasse, A. Syrel. http://files.pharo.org/books-pdfs/booklet-Bloc/2017-11-09-memorygame.pdf To load the memory game Metacello new baseline: 'BlocTutorials'; repository: 'github://pharo-graphics/Tutorials/src'; load A similar booklet could be done for the title 'Doing a presentation / slide show / assitant with Bloc' (or similar, adapt .....)

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Article about PowerPoint and Smalltalk
by askoh Nov. 21, 2017

Nov. 21, 2017

https://spectrum.ieee.org/tech-history/cyberspace/the-improbable-origins-of… I like the end "Meanwhile, the dominant mode of personal computing globally has firmly shifted from the desktop and laptop to the smartphone. As yet, no new vision of personal computing like the one that came from Xerox PARC in the 1970s has emerged. And so for the moment, it appears that PowerPoint, as we know it, is here to stay." Aik-Siong Koh -- Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html

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RBRuleIfNotNilDo usage
by Alistair Grant Nov. 21, 2017

Nov. 21, 2017

Hi Everyone, I'm loading some code in to Pharo 7 that tries to use #ifNotNilDo:. There's already a transformation to re-write it to the correct #ifNotNil: - RBRuleIfNotNilDo. How can I apply the transformation to all existing methods in the image that call #ifNotNilDo:? Thanks, Alistair

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Roassal2 breaks Pharo 7
by Alistair Grant Nov. 21, 2017

Nov. 21, 2017

Hi Everyone, Loading Roassal 2 in Pharo 7 with: Gofer it smalltalkhubUser: 'ObjectProfile' project: 'Roassal2'; configurationOf: 'Roassal2'; loadStable. makes the image unusable due to changes in NewValueHolder. Roassal adds: NewValueHolder>>announcer ^ announcer which is fine in Pharo 6 because NewValueHodler is a subclass of Object and initialises announcer in #initialize. In Pharo 7 NewValueHolder is a subclass of Model and relies on lazy initialisation of announcer in the corresponding accessor method inherited from Model. But... since Roassal is overriding the accessor method, announcer is never initialised, with the result that errors similar to: UndefinedObject(Object)>>doesNotUnderstand: #announce: are triggered (often enough that the image is largely unusable). I think the solution is to modify the packaging so that NewValueHolder>>announce is moved in to a separate package that is only loaded in Pharo 6 and earlier. Thoughts? Thanks! Alistair

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Re: [Pharo-users] Timespan translateToUTC problematic (Alistair Grant)
by Richard A. O'Keefe Nov. 21, 2017

Nov. 21, 2017

> From: Alistair Grant <akgrant0710(a)gmail.com> > I think that there's still use for representing a date as a timespan, > i.e. a 24 hour period that we can use to find the intersection of > times, etc (in addition to adding a timezone offset to a DateTime to > figure out the date in a different country). Whether it needs to be a > separate class from Timespan I'm not so sure. From my Smalltalk library: Date methods: asMidnightDateAndTime ^DateAndTime year: self year month: self month day: self dayOfMonth hour: 0 minute: 0 second: 0 pvtSpanFrom: start to: end ^Timespan starting: start asMidnightDateAndTime ending: end asMidnightDateAndTime daySpan ^self pvtSpanFrom: self to: self next monthSpan ^self pvtSpanFrom: self thisMonth to: self nextMonth quarterSpan ^self pvtSpanFrom: self thisQuarter to: self nextQuarter yearSpan ^self pvtSpanFrom: self thisYear to: self nextYear One of the tricky things here is that the result of #daySpan may be 23, 24, or 25 hours, plus or minus a second depending where the leap seconds fall. It is *usually* a 24-hour period, but definitely not always. And of course you can't go *back* from a #daySpan to a Date without reference to a particular time zone (not zone offset, because of course the zone offset can change during a "day").

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Re: [Pharo-users] New Pharo article at The Cohort
by Richard A. O'Keefe Nov. 20, 2017

Nov. 20, 2017

I'm obviously missing a lot of the context here, but in my country (New Zealand) there is something called the Fair Trading Act. My understanding from reading the Commerce Commission web site is that - false or misleading representations about goods or services or the availability of goods are against the law - "The penalties for breaching the Act can be severe" (Grant Harris). - obviously wild exaggerations made to be funny are sort of OK, but if anyone falls for them you could find this tested in court - "Any claims made to bolster the image of a business or its products or services must be accurate." - "The Act applies even when there was no intention to breach the Act". (Grant Harris again.) http://www.comcom.govt.nz/fair-trading/fair-trading-act-fact-sheets/claimin… The Fair Trading Act was passed as part of a program of market liberalisation and in order to foster competition and market efficiency, and the majority of the cases have been trader-to- trader. Why mention this? Because it's not just places where consumer protection is high-ranked that have such laws; it's also places that are gung-ho about free markets and competition and want to protect businesses. Law in the USA varies from state to state. For California, see https://www.truthinadvertising.org/california/ (which has a navbar on the right for other states). Me, I think Pharo is good enough to "sell" on its merits without any exaggerations. (If you could combine the great looks of Dolphin Smalltalk with the great features of Pharo, drool...)

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Re: [Pharo-users] Timespan translateToUTC problematic
by Richard A. O'Keefe Nov. 20, 2017

Nov. 20, 2017

I think the fundamental question is what a Date is supposed to represent. I have spent a LOT of time thinking about date and time classes over the last 10 years, and have come to the conclusion that it makes no sense to view a Date as a Timespan. Let's take an example. Christmas this year is going to be 2017-12-25 in every country that uses the Gregorian calendar and observes Christmas at all. If I ask the question "Is Christmas on the same date in Utah as it is in Otago?" I expect to get the answer YES. But if I ask the question "Is the span of time *called* Christmas day there same as the span of time *called* Christmas day here?" I expect to get the answer NO. It's not entirely unlike the way that '95 Hanover Street' is the same street address in my city as '95 Hanover Street' in Edinburgh, but they correspond to quite different places. (Here: the Urgent Doctors; there: serviced apartments.) Returning to Dates, I expect something like aDate asTimespan: aTimeZone to return a timespan that might be 23, 24, or 25 hours (possibly plus an extra second), with *maybe* aDate asTimespan meaning aDate asTimespan: TimeZone here Naturally the same goes for Weeks, Months, and Years, should they exist.

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New Pharo article at The Cohort
by horrido Nov. 19, 2017

Nov. 19, 2017

Why Pharo Might be the Future of Software Development <https://blog.appacademy.io/pharo-future-software-development/> Spread the word. -- Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html

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Grease for Pharo7: TBehavior extensions?
by Johan Brichau Nov. 19, 2017

Nov. 19, 2017

Hi Pharoers, We have one failing test for Grease in Pharo7. The reason is that Grease extends the TBehavior trait with a method #fullName. I notice this trait is no longer used? Are we supposed to extend Behavior directly? Overall: what are the plans? Some advice would be good so I can keep Grease into shape. thanks everyone Johan

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