March 2022 - Pharo-users - lists.pharo.org

Re: Null Object Pattern

by Tim Mackinnon

This has been an interesting thread to read on the side, and I appreciate the thought provoking conversion. On Sun, 20 Mar 2022, at 6:11 AM, Richard O'Keefe wrote: > An override of #doesNotUnderstand: *is* (an instance of) the problem. > What part of "you may think you know what to forward now, but just > wait a couple of months or install an additional package and there > will be *more* selectors you needed to think about but didn't" is > hard to understand? However I am confused by the above - as in Pharo and Dolphin (and I suspect other Smalltalks) - you don't have to make your proxy a subclass of Object right? If you want to forward as much behaviour as possible - you can subclass ProtoObject (or equivalent). The width of methods on that is much reduced (59 from a quick glance), and loading other packages doesn't tend to extend at that level, so keeping things much more stable. The downside, is that such objects are tricky to view in an inspector etc. There is a mocking framework in Pharo called Ghost that leverages this quite well from memory. So I think that some of the side arguments on downsides might not be quite as bad as indicated. Tim

March 21, 2022

Re: Null Object Pattern

by James Foster

Richard, My primary reference for the Proxy Pattern is the classic "Design Patterns, Elements of Reusable Object-Oriented Software" by Gamma, Helm, Johnson, and Vlissides (Addison-Wesley 1995). In describing how to implement the pattern the âGang of Four (or GOF)" advise âusing doesNotUnderstand in Smalltalkâ (p. 212). Furthermore, as to typing, they say that âProxy doesnât always have to know the type of real subjectâ (213). The GOF anticipated the problem with inlined selectors and caution that âa few special messages ... are handled directly by the virtual machine [and] do not cause the usual method look-upâ (p. 212). So, I think it is reasonable, in the context of a discussion of the Proxy Pattern, to suggest that the Proxy Pattern would be more effective with fewer inlined selectors. As to where the Proxy Pattern was developed, the GOF describe âKnown Usesâ including remote objects in NEXTSTEP (1994) and in Smalltalk (1987). In the remote object context, a Proxy has no need to know the type of the target, it just needs to know how to forward messages and return results. While there is typically a way to find out if something is a proxy or not (e.g., #â_isProxyâ) the beauty of the Proxy Pattern is that you donât have to rewrite the entire application and use something like #âapparentClassâ or #âapparentlyNilâ. Only the parts of the application that care if you have a proxy (which will typically not be the main domain code) need to look more deeply (with special selectors or reflection). It appears that you believe that a untyped proxy to a remote object is bad and that all the code in an application should be written to be aware of the possible âremotenessâ of certain objects. It is my understanding that a transparent untyped proxy to a remote object is well-accepted, extremely useful, and can be implemented reliably. I donât think I can contribute much more to the conversation than that so Iâll leave it there. Regards, James > On Mar 20, 2022, at 4:55 PM, Richard O'Keefe <raoknz(a)gmail.com> wrote: > > Never forget that the Proxy pattern was developed in the context of a TYPED programming > language. So "Clients can't tell whether they work with a subject or its proxyâ means WITH REFERENCE > TO A STATED PROTOCOL. Doing this in Ada or Java is fine, because you define an interface type, and that > makes it safe. Here is a sentence from a typical description of the pattern: "Since the proxy implements the > INTERFACE as the original class, it can be passed to any client that expects a real service object." Having > a specified and *enforced* smallish interface prevents the maintenance issues that plague attempts to use > this pattern in Smalltalk. > > Remote objects and local objects have different semantics because remote messages and local messages > have different semantics. Local messages cannot be lost, duplicated, or reordered, nor can communication > with a local object drop out for no local reason. Version skew is a much bigger problem with distributed > systems than local ones, so once again, it is proxying WITH REFERENCE TO A STATED PROTOCOL (and > that not a large one!) that counts. There is no such thing as a 100% transparent remote proxy. So it is > very useful to know what an object really is as well as what it pretends to be. That is, > #class #apparentClass > #isNil #apparentlyNil > are *different*, > > So the argument thus far is > - a selector should not be inlined if it might need to be overridden > - such as in an application of the Proxy pattern > - but well-designed Proxies are such WITH REFERENCE TO STATED PROTOCOLS > - meaning that selectors that are NOT in such protocols are fair game for inlining. >

March 21, 2022

Positions at lifeware :)

by stephane ducasse

March 21, 2022

Re: Another question about Spec2 and SpTablePresenter

by Mark O'Donoghue

Hi Esteban Many thanks for your help on this. A. I managed to get it working with a small change â which looks like it was due to issue 1263 as you indicated And this technique was successful my main application too. Next, I will load the latest merge for Spec2 and do it properly. âTest class>>esteban <example> | items | items := { #one -> 'one'. #two -> 'two' }. table := SpTablePresenter new addColumn: (SpStringTableColumn title: 'Key' evaluated: #key); addColumn: (SpStringTableColumn new title: 'Value'; evaluated: #value; beEditable; onAcceptEdition: [ :item :newValue | item value: (newValue getText string) ]; yourself). table items: items. table openWithSpec .â B. Do you think there is any merit in using a notifications design approach in this example? (e.g. using âmodel changedâ)? (That was my first instinctâ¦but I couldnât see how to do it.) If you think that makes sense, does Spec2 have the hooks required to do it this way? C. My comment on documentation was a good hearted grumble - and is not about the source code... I think the community urgently needs guides like the âAn Introduction to user interface building with Spec 2.0â â this one is still WIP after many months. The trial and error learning curve for all the part timers like me is very inefficient and frustrating. I understand manpower and time are seriously limiting factors, but more good learning resources would really help wider adoption of Pharo IMHO. Thatâs just useful feedback I hopeâ¦ ð Again, many thanks for your help. Cheers Mark, Perth WA From: Esteban Lorenzano <estebanlm(a)netc.eu> Sent: Sunday, 20 March 2022 10:15 PM To: Any question about pharo is welcome <pharo-users(a)lists.pharo.org> Cc: pharo-users(a)lists.pharo.org Subject: [Pharo-users] Re: Another question about Spec2 and SpTablePresenter Hi, well, the incomplete documentation of Spec states clearly that you will be receiving two parameters: onAcceptEdition: aBlock "Set the block to execute when cell edition is accepted. `aBlock` receives two arguments: - the element of the table (See `SpAbstractListPresenter>>#items:` - the string entered while editing" acceptAction := aBlock So, when you set beEditable to your column, you can do something like this: items := { #one -> 'one'. #two -> 'two' }. table := SpTablePresenter new addColumn: (SpStringTableColumn title: 'Key' evaluated: #key); addColumn: (SpStringTableColumn new title: 'Value'; evaluated: #value; beEditable; onAcceptEdition: [ :item :newValue | item value: newValue ]; yourself); items: items; open. and then you can edit whatever you want and update your item. Now, since this is a mechanism that has not been used a lot yet in morphic backend, I just discovered and fixed a bug (not in editable tables, but that affects it: https://github.com/pharo-spec/Spec/issues/1263) so if you want to actually use the functionality, you will need to wait until is merged (tomorrow). Esteban On Mar 20 2022, at 10:26 am, Mark O'Donoghue <mark.odonoghue.2010(a)gmail.com <mailto:mark.odonoghue.2010@gmail.com> > wrote: Howdy all I am making progress with quite a large application which relies heavily on Spec2 ( but Spec2 is such a big learning curve for me â especially given the incomplete documentationâ¦ ð) I am currently struggling with the following issue: I have a SpTablePresenter which shows a collection of domain objects (subclassed from Model). The domain object are instances of âAssetâ which is a relatively simple class. The table works fine. Now, I need to be able to update some columns , but I donât think I want to build a separate form for doing classic CRUD operations. (There is no need for create or delete functionality â so an in-situ update seems desirableâ¦). Iâve made a start using SpStringTableColumn >> beEditable and #onAcceptEdition: But I canât see how to work out what row and column has changed, and how I can update the corresponding Asset instance(s). It thought it would be handled using #whenModelChanged: but there are models in many places (and at several levels in the Spec hierarchy)â¦ Iâve tried following it all the way down to the adapters and morphs but I canât see how the freshly edited cell interacts with the model or announcements. (BTW - It doesnât look like the âselected itemâ features are appropriate since you can do edits in other rows regardless of what row is/isnât selected.) Is there a correct and/or elegant way to detect these cell changes in a SpTablePresenter and apply them to my domain objectsâ¦? Cheers Mark From: Mark O'Donoghue <mark.odonoghue.2010(a)gmail.com <mailto:mark.odonoghue.2010@gmail.com> > Sent: Sunday, 4 July 2021 5:26 PM To: pharo-users(a)lists.pharo.org <mailto:pharo-users@lists.pharo.org> Subject: Question about Spec2 and SpTablePresenter Howdy all Iâve got stuck trying to manage Tables â over 12 hours now and Iâm out of ideas!. â¹ Any observations / suggestions are most welcomeâ¦ Iâve been loading small external files of transactions using NeoCSV into Spec2 tables. I am trying to use Fuel to persist the table contents so that my application will re-load the working state from where I finished in the last session. (Iâve opted for Fuel as a simple alternative to having to do the whole object relational mapping thing.) The idea is that transactions (and potentially some manual adjustments) will be processed over time. (This is preferable to having to reload all files from the beginning evert time I run the applicationâ¦) The Spec2 tables have been working well until I tried to persist them. I canât seem to fully re-load them to a previously saved state. For example - I can restore the essential contents of my table in most circumstances using: restoreObjects âfilePresenter1 is a SpTablePresenterâ | objects savedEntry | objects := CpPersist restoreObjectsFromFileNamed: 'E:\Me\zzzST-Test\demo.fuel'. recentFileList := objects at: 1. currFileFilter := objects at: 2. savedEntry := objects at: 3. self updateFilterButton: currFileFilter. filteredFileList := self filterFilesUsing: currFileFilter. filePresenter1 items: filteredFileList. savedEntry ifNotNil: [filePresenter1 selectItem: savedEntry ]. However, if any of the table columns are re-sorted , the re-load operation gets confused and I canât get the saved a saved selected item to become selected again. (It seems to be confusing the index numbers of the sorted and unsorted lists â even when I match by contents rather than index.) (I also created an equality test to ensure equivalent entries are recognised by the #= operation in the list of the underlying model ). This all works fine - unless I sort a column! Since this approach was going to be used on several screens Iâd really like to find a solution. Cheers Mark Perth, Western Australia

March 21, 2022

Re: Null Object Pattern

by Richard O'Keefe

Never forget that the Proxy pattern was developed in the context of a TYPED programming language. So "Clients can't tell whether they work with a subject or its proxyâ means WITH REFERENCE TO A STATED PROTOCOL. Doing this in Ada or Java is fine, because you define an interface type, and that makes it safe. Here is a sentence from a typical description of the pattern: "Since the proxy implements the INTERFACE as the original class, it can be passed to any client that expects a real service object." Having a specified and *enforced* smallish interface prevents the maintenance issues that plague attempts to use this pattern in Smalltalk. Remote objects and local objects have different semantics because remote messages and local messages have different semantics. Local messages cannot be lost, duplicated, or reordered, nor can communication with a local object drop out for no local reason. Version skew is a much bigger problem with distributed systems than local ones, so once again, it is proxying WITH REFERENCE TO A STATED PROTOCOL (and that not a large one!) that counts. There is no such thing as a 100% transparent remote proxy. So it is very useful to know what an object really is as well as what it pretends to be. That is, #class #apparentClass #isNil #apparentlyNil are *different*, So the argument thus far is - a selector should not be inlined if it might need to be overridden - such as in an application of the Proxy pattern - but well-designed Proxies are such WITH REFERENCE TO STATED PROTOCOLS - meaning that selectors that are NOT in such protocols are fair game for inlining.

March 20, 2022

Re: Null Object Pattern

by James Foster

Hello Richard, > What part of â¦ is hard to understand? Did you mean for this to come off as condescending? Or are you are honestly wondering how effectively you are communicating? In either case, all of it is hard for me to understand since it doesnât describe the Proxy Pattern which requires that "Clients can't tell whether they work with a subject or its proxyâ (https://en.wikipedia.org/wiki/Proxy_pattern <https://en.wikipedia.org/wiki/Proxy_pattern>). My understanding of a proxy is that it will rarely/never happen that "there will be *more* selectors you needed to think about but didnât." So, far from being (an instance of) the problem, an override of #âdoesNotUnderstand:â is the elegant solution. > I wanted something that was like an OrderedCollection but could only hold elements of a specific class. It seems what you want is not a Proxy but a Facade (https://en.wikipedia.org/wiki/Facade_pattern <https://en.wikipedia.org/wiki/Facade_pattern>) in which you "may perform additional functionality [such as type checking] before ... forwarding a requestâ (https://en.wikipedia.org/wiki/Facade_pattern <https://en.wikipedia.org/wiki/Facade_pattern>). > I *could* make a proxy by going through #doesNotUnderstand: but I am not going to. Thatâs fine, and a proxy is probably inappropriate for the things you do. But there are a few usage scenarios <https://en.wikipedia.org/wiki/Proxy_pattern#Possible_usage_scenarios> where they are appropriate. My primary experience with them is with distributed object communication <https://en.wikipedia.org/wiki/Distributed_object_communication> where they are appropriate. > I *could* make a batch of ricin and store it in my granddaughter's bedroom, but I'm not going to. Iâm glad to hear it. To take a more realistic example, I could try to fly a 747 but Iâm not going to (since my commercial pilotâs license doesnât include that rating). That doesnât mean that no one should fly a 747 (or implement a Proxyâthe people who make GemBuilder for Smalltalk <https://gemtalksystems.com/products/gbs-vw/> should certainly use proxies). I remember hearing a joke about Kent Beck holding a sign saying âWill override #doesNotUnderstand: for foodâ! I took it as not saying that only a genius can understand DNU but that you should think carefully about how it will be used (and in many cases something else would be appropriate). Everything else about Kent Beckâs work makes it clear that leaving behind clear maintainable code is a top priority. James > On Mar 19, 2022, at 11:11 PM, Richard O'Keefe <raoknz(a)gmail.com> wrote: > > An override of #doesNotUnderstand: *is* (an instance of) the problem. > What part of "you may think you know what to forward now, but just > wait a couple of months or install an additional package and there > will be *more* selectors you needed to think about but didn't" is > hard to understand? > > Proxies done right are proxies *relative to a specified protocol*. > > Let me give you a personal example. > I wanted something that was like an OrderedCollection but > could only hold elements of a specific class. > No worries, just make a proxy. Make a bare-bones object, > define all the #add... methods to check their argument, > and use #doesNotUnderstand to forward everything else to > the underlying OrderedCollection. > > The first problem is the selectors that the bare-bones > object *does* understand by virtue of being an object. > (Remember there are *hundreds* of these selectors in > Squeak, Pharo, VisualWorks, even in gst there are more > than 120). You must, for example, ensure that #instVarAt: > is forwarded, not handled locally, BUT you must also > ensure that #instVarAt:put: is handled locally, not forwarded. > And then one day you find that your program has broken, > because mutable collections now have > aMutableCollection inPlaceCollect: collectBlock > and that can put unacceptable results in the collection > *without* going through any #add... method. > > Eventually you realise "handing out a wrapper for this > collection constrained to only allow adding certain things" > is the wrong way to do it, and you do something like > > constrainedAdder: constraint > ^[:x | (constraint value: x) > ifTrue: [self add: x] > ifFalse: [DomainError receiver: self selector: #add:]] > > or you do something else entirely, like handing out a wrapper with > a *narrow* interface that doesn't make the slightest pretence of > *being* the other object. > > I *could* make a batch of ricin and store it in my > granddaughter's bedroom, but I'm not going to. > I *could* make a proxy by going through #doesNotUnderstand: > but I am not going to. That would be a textbook example of > maxim 38: "Just because it's easy for you doesn't mean it > can't be hard on your clients." > > > > > > > On Sun, 20 Mar 2022 at 15:18, James Foster <smalltalk(a)jgfoster.net <mailto:smalltalk@jgfoster.net>> wrote: > I donât understand. Wouldnât an override of #'doesNotUnderstand:â solve this problem? The proxies Iâve seen subclass from nil or ProtoObject and forward almost everything to the target. Itâs really very easy. > >> On Mar 19, 2022, at 3:14 AM, Richard O'Keefe <raoknz(a)gmail.com <mailto:raoknz@gmail.com>> wrote: >> >> An object should be a Proxy or Stub only with reference to a specific protocol, which should be kept narrow. >> >> Being a Proxy is a form of coupling. Proxying a wide >> interface creates maintenance problems: >> Squeak 5.3 : Object selectors size => 485 >> Pharo 9.0 : Object selectors size => 435 >> astc : Object selectors size => 325 >> VW 8.3PUL : Object selectors size => 304 >> >> The interface of Object is HUGE. You want to bet that >> your Proxy got *all* of the methods right? This >> interface didn't get that way all at once; it grew. >> The number was 78 in Smalltalk-80. At a minimum, then, >> Smalltalk systems have accreted one extra Object method >> every two months. >> >> So you set up your proxy to *flawlesly* mirror Object, >> and then, WHOOPS, upgrade Smalltalk and now there is a >> method that Object has and your Proxy either lacks (if >> it descends from ProtoObject but not Object) or inherits >> an inappropriate version of (if it descends from Object). >> >> What this means is that nobody ever *does* flawlessly >> mock everything in the public interface of an object >> they are Proxying. They proxy a *limited* protocol. >> Because that is all they *can* do. >> >> Look, I know that people who have been trained to work >> with the stuff can use C4 as cooking fuel. But I haven't >> had that training, so I won't touch the stuff. In the >> same way, I dare say there are things *you* can safely >> do in Smalltalk that fumblefingers here would be burnt >> badly by. There are many things that *can* be done that >> I *won't* do. In a chemistry lab, I would not work with >> ClF3 let alone O2F2. In Smalltalk, I don't monkey with >> #isNil. >> >> On Fri, 18 Mar 2022 at 03:52, James Foster <smalltalk(a)jgfoster.net <mailto:smalltalk@jgfoster.net>> wrote: >> Richard, >> >> I very much admire Dijkstraâs admonition regarding âThe Humble Programmerâ and was pointing a student to that article just this week. >> >> In any case, I think youâve demonstrated that you now comprehend the argument against inliningâyou just donât agree. Thatâs fair and I think the discussion has been clarified. Would it be fair to say that you have an âideological objectionâ to allowing a Proxy or Stub to transparently stand in for another object (say, in a two-object-space environment such as Pharo and GemStone)? That is, a domain object canât be replaced by a Proxy or Stub without a wholesale rewrite of the rest of the application? I respect that as a reasonable position (demanding perfect clarity), but I see a cost to that position as well. >> >> Of course, if you really want to avoid allowing the receiver to chose its response to a message, you can use other messages. So if you want to find out if an object is identical to nil you should use `nil == myObject` to ensure that there was not an override of #âisNilâ or #â==â by the objectâs class. >> >> James >> >>> On Mar 17, 2022, at 2:27 AM, Richard O'Keefe <raoknz(a)gmail.com <mailto:raoknz@gmail.com>> wrote: >>> >>> My chief concern is that I am a bear of very little brain, >>> and if you change the meaning of #isNil to anything at all >>> other than "is the receiver identical to nil" you *WILL* >>> (not may) confuse me. This extends to things that happen >>> not to be inlined: if even a god-like Smalltalker like >>> Andres Valloud overloads #, to something other than "combine >>> the collection that is the receiver with the collection that >>> is the argument to yield a new collection" than I *WILL* >>> most certainly be confused and find the code unmaintainable. >>> Smalltalk being Smalltalk, if you admit an inconsistent >>> overload anywhere, I can no longer understand sends of that >>> selector anywhere. One of the things to like about Traits >>> is that you can say "this class doesn't just *happen* to >>> have selectors x and y, it has them *because* it has this >>> whole consistent bundle of selectors." >>> >>> There are more annotations documented for my Smalltalk >>> compiler than are actually implemented. One that *is* >>> implemented is <doNotOverride>, and it has caught more >>> mistakes than I care to admit to. It's particularly >>> important for a bundle of methods with varying arguments >>> that are meant to be routed through a single method, >>> which *is* meant to be overridden. It makes sure that >>> I override the *right* method. (Take #= and #~= as an >>> obvious example.) >>> >>> Once you start down the path of lying about things like #isNil >>> you find that EITHER you have to go very far down that path >>> and override #== and #instVarAt: and a whole lot of other >>> things OR you are working with a semantically incoherent system. >>> >>> "How should a proxy (https://en.wikipedia.org/wiki/Proxy_pattern <https://en.wikipedia.org/wiki/Proxy_pattern>) to nil respond to the #âisNilâ message?" >>> >>> It SHOULD NOT LIE. A proxy *isn't* nil, and it doesn't *behave* like nil, >>> even if it is a proxy for nil. A proxy, qua proxy, can do things that nil >>> cannot. Use another selector, #isEffectivelyNil, or whatever reveals your >>> intentions, and give it what semantics you find useful. >>> >>> "How should the Null Object Pattern (https://en.wikipedia.org/wiki/Null_object_pattern <https://en.wikipedia.org/wiki/Null_object_pattern>) respond to #âisNilâ?" >>> >>> It should answer false. Period. No ifs, buts, quibbles, or maybes. >>> The whole *point* of the Null Object Pattern is to return something >>> that *isn't* nil, that has quite a different protocol. If you call >>> something that is supposed to return either a Foo or a NullFoo, and >>> it gives you nil instead, there is a BUG in what you just called so >>> the sooner you find out the better. What you want is >>> >>> Foo >> isNullFoo ^false >>> NullFoo >> isNullFoo ^true >>> and no other class defines #isNullFoo. >>> >>> That way, when you ask "tripeWorks grobblingMill lastPallet isNullPallet" >>> (a) you make it clear to someone reading your code what you are expecting >>> (b) if you DON'T get what you are expecting, Smalltalk will tell you. >>> >>> I must admit that on the few occasions when I've used Null Object >>> I've used an all-purpose #isMissing instead of a task-appropriate >>> #isNullFoo, but then I figured out what I was doing wrong. You >>> look at the code, you say "there's *something* off here, but I don't >>> know what." But when you ask "what, exactly, does this method MEAN?" >>> you realise "oh, THAT'S what I was doing wrong." #isMissing told me >>> it was a NullPerson or a NullAddress or a NullPartsList or ... but >>> in this case I needed to know whether it was a NullSummary. >>> >>> And of course you run into E.F.Codd's lesson: "one NULL is never >>> enough, information can be missing for more than one reason". >>> Take the familiar example of a phone number: >>> - I know that Fred's phone number is X >>> - I know that Fred has a phone but I don't know what the number is >>> - I don't know whether Fred has a phone or not >>> - I know that Fred has no phone >>> There's room for three *different* null objects there. >>> Should we have UnknownNumberOfActualPhone to answer false to #isnil >>> and NonNumberOfNonexistentPhone to answer true? Or what? >>> >>> By the way, you may have misunderstood my benchmark. >>> It wasn't that #isNil or even _ ifNotNil: speeded up by >>> 10%, it was the *whole* matrix-munching benchmark that >>> speeded up. Certainly not a big deal, but it's not >>> something I'd be happy to give up in order to get less >>> maintainable code. >>> >>> >>> >>> >>> >>> >>> >>> >>> On Thu, 17 Mar 2022 at 18:21, James Foster <smalltalk(a)jgfoster.net <mailto:smalltalk@jgfoster.net>> wrote: >>> Richard, >>> >>> My _concern_ with inlining is that since it is designed to short-circuit dynamic method lookup, it is impossible to call a _different_ implementation. That is, you lose the opportunity to have the _receiver_ decide how to respond to the message. You may think of it as a message, but the caller is deciding how the receiver will respondâwhich largely defeats the purpose and role of it being a message. Yes, at the machine code level you are performing a branch instruction, but when comparing OOP to Procedural Programming we typically make a distinction between âmessagesâ and "procedure calls." The distinction is that the receiver gets to decide how to respond to a message. In C++ this is the distinction between a âvirtual" and "non-virtual" function. By inlining, you are converting the function from a virtual function to a non-virtual function, and this can make a difference (which is why virtual functions exist). >>> >>> How should a proxy (https://en.wikipedia.org/wiki/Proxy_pattern <https://en.wikipedia.org/wiki/Proxy_pattern>) to nil respond to the #âisNilâ message? How should the Null Object Pattern (https://en.wikipedia.org/wiki/Null_object_pattern <https://en.wikipedia.org/wiki/Null_object_pattern>) respond to #âisNilâ? >>> >>> And, yes, Iâm sure you can come up with benchmarks that show a measurable difference, but what is the impact in realistic code? When someone asked about inlining #âyourselfâ in GemStone I believe I measured the performance as taking 2 nanoseconds per call (on a 2012 machine). A 10% speedup would make it 1.8 nanoseconds. Is that worth it? Maybe, maybe not. >>> >>> Note that I described my position as a âconcern,â not an ideological objection. Mostly Iâm giving a rationale for something that doesnât seem to be explained very well for you. I accept that there may be a time for inlining, but I can âcomprehend" another side to the issue. >>> >>> James >>> >>>> On Mar 16, 2022, at 9:42 PM, Richard O'Keefe <raoknz(a)gmail.com <mailto:raoknz@gmail.com>> wrote: >>>> >>>> We're still not on the same page. >>>> You seem to have some ideological objection to inlining that >>>> I am completely failing to comprehend. >>>> Just because a procedure call (message send) is inlined doesn't >>>> in the least mean it *isn't* a procedure call (message send), >>>> just as compiling a procedure call (message send) as a jump >>>> (last-call optimisation) doesn't mean it *isn't* a procedure >>>> call (message send). >>>> By the way, forget about "40 years ago". >>>> I just did an experiment in Pharo 9, and found that >>>> using "_ ifNotNil: " instead of "_ izNil ifFalse: " >>>> -- where izNil is a non-inlined self == nil -- >>>> gave a 10% speedup, in a test code where real work was going >>>> on as well. >>>> As for turning off all inlining, what do you think that would >>>> do to #ifFalse:ifTrue: and its relatives? >>>> >>>> >>>> On Thu, 17 Mar 2022 at 08:34, <sean(a)clipperadams.com <mailto:sean@clipperadams.com>> wrote: >>>> >>>> >>>> To start with, why do you CARE whether a particular method is inlined or not? >>>> >>>> I care because it makes âeverything is a messageâ a lie! And I suspect (no proof and could be wrong) itâs an optimization that only made sense with the hardware constraints of 40+ years ago. Arguing against premature optimization is hardly something I just made up ;-) >>>> >>>> This makes absolutely no sense to me. What makes you think that the combination "_ isNil ifFalse: [_]" will NOT be inlined? >>>> >>>> I may have been unclear. My intent was to communicate: âIâd like to stop ALL* inlining of messages by default if possibleâ >>>> >>>> *or as many as practical >>>> >>>> The thing that rings loud alarm bells for me is there being "long chains" in the first place. >>>> >>>> I agree that it is in general a smell, but long chains was tangential to the intention above >>>> >>>> Can you give an example? >>>> >>>> I donât know if I can think of one thatâs not contrivedâ¦ Wrapping something external? Squeakâs AppleScript support used to mirror the underlying AS, which is pretty much exactly that. >>>> >>>> In my own programming, I've generally found that nils turning up in the middle of a chain indicates a serious design error somewhere. >>>> >>>> Agreed. See smell comment above. >>>> >>> >> >

March 20, 2022

Re: Another question about Spec2 and SpTablePresenter

by Esteban Lorenzano

uh, for some reason my mail client eat the formatting... but you get the idea ;) On Mar 20 2022, at 3:14 pm, Esteban Lorenzano <estebanlm(a)netc.eu> wrote: > Hi, > > well, the incomplete documentation of Spec states clearly that you will be receiving two parameters: > onAcceptEdition: aBlock > "Set the block to execute when cell edition is accepted. > `aBlock` receives two arguments: > - the element of the table (See `SpAbstractListPresenter>>#items:` > - the string entered while editing" > acceptAction := aBlock > > So, when you set beEditable to your column, you can do something like this: > items := { #one -> 'one'. #two -> 'two' }. > table := SpTablePresenter new > addColumn: (SpStringTableColumn title: 'Key' evaluated: #key); > addColumn: (SpStringTableColumn new > title: 'Value'; > evaluated: #value; > beEditable; > onAcceptEdition: [ :item :newValue | item value: newValue ]; > yourself); > items: items; > open. > and then you can edit whatever you want and update your item. > > Now, since this is a mechanism that has not been used a lot yet in morphic backend, I just discovered and fixed a bug (not in editable tables, but that affects it: https://github.com/pharo-spec/Spec/issues/1263) so if you want to actually use the functionality, you will need to wait until is merged (tomorrow). > Esteban > > On Mar 20 2022, at 10:26 am, Mark O'Donoghue <mark.odonoghue.2010(a)gmail.com> wrote: > > Howdy all > > > > > > I am making progress with quite a large application which relies heavily on Spec2 > > ( but Spec2 is such a big learning curve for me â especially given the incomplete documentationâ¦ ð) > > > > I am currently struggling with the following issue: > > I have a SpTablePresenter which shows a collection of domain objects (subclassed from Model). > > The domain object are instances of âAssetâ which is a relatively simple class. > > The table works fine. > > > > Now, I need to be able to update some columns , but I donât think I want to build a separate form for doing classic CRUD operations. > > (There is no need for create or delete functionality â so an in-situ update seems desirableâ¦). > > > > Iâve made a start using SpStringTableColumn >> beEditable and #onAcceptEdition: > > > > But I canât see how to work out what row and column has changed, and how I can update the corresponding Asset instance(s). > > It thought it would be handled using #whenModelChanged: but there are models in many places (and at several levels in the Spec hierarchy)â¦ > > Iâve tried following it all the way down to the adapters and morphs but I canât see how the freshly edited cell interacts with the model or announcements. > > > > (BTW - It doesnât look like the âselected itemâ features are appropriate since you can do edits in other rows regardless of what row is/isnât selected.) > > > > Is there a correct and/or elegant way to detect these cell changes in a SpTablePresenter and apply them to my domain objectsâ¦? > > > > Cheers > > Mark > > > > > > > > > > From: Mark O'Donoghue <mark.odonoghue.2010(a)gmail.com> > > Sent: Sunday, 4 July 2021 5:26 PM > > To: pharo-users(a)lists.pharo.org > > Subject: Question about Spec2 and SpTablePresenter > > > > > > > > > > > > Howdy all > > > > Iâve got stuck trying to manage Tables â over 12 hours now and Iâm out of ideas!. â¹ > > > > Any observations / suggestions are most welcomeâ¦ > > > > Iâve been loading small external files of transactions using NeoCSV into Spec2 tables. > > I am trying to use Fuel to persist the table contents so that my application will re-load the working state from where I finished in the last session. > > (Iâve opted for Fuel as a simple alternative to having to do the whole object relational mapping thing.) > > > > The idea is that transactions (and potentially some manual adjustments) will be processed over time. > > (This is preferable to having to reload all files from the beginning evert time I run the applicationâ¦) > > > > The Spec2 tables have been working well until I tried to persist them. > > I canât seem to fully re-load them to a previously saved state. > > > > For example - I can restore the essential contents of my table in most circumstances using: > > > > restoreObjects > > > > âfilePresenter1 is a SpTablePresenterâ > > > > | objects savedEntry | > > > > objects := CpPersist restoreObjectsFromFileNamed: 'E:\Me\zzzST-Test\demo.fuel'. > > > > recentFileList := objects at: 1. > > currFileFilter := objects at: 2. > > savedEntry := objects at: 3. > > > > self updateFilterButton: currFileFilter. > > > > filteredFileList := self filterFilesUsing: currFileFilter. > > > > filePresenter1 items: filteredFileList. > > > > savedEntry > > ifNotNil: [filePresenter1 selectItem: savedEntry ]. > > > > > > However, if any of the table columns are re-sorted , the re-load operation gets confused and I canât get the saved a saved selected item to become selected again. > > > > (It seems to be confusing the index numbers of the sorted and unsorted lists â even when I match by contents rather than index.) > > (I also created an equality test to ensure equivalent entries are recognised by the #= operation in the list of the underlying model ). > > > > This all works fine - unless I sort a column! > > > > Since this approach was going to be used on several screens Iâd really like to find a solution. > > > > Cheers > > Mark > > Perth, Western Australia

March 20, 2022

Re: Another question about Spec2 and SpTablePresenter

by Esteban Lorenzano

Hi, well, the incomplete documentation of Spec states clearly that you will be receiving two parameters: onAcceptEdition: aBlock "Set the block to execute when cell edition is accepted. `aBlock` receives two arguments: - the element of the table (See `SpAbstractListPresenter>>#items:` - the string entered while editing" acceptAction := aBlock So, when you set beEditable to your column, you can do something like this: items := { #one -> 'one'. #two -> 'two' }. table := SpTablePresenter new addColumn: (SpStringTableColumn title: 'Key' evaluated: #key); addColumn: (SpStringTableColumn new title: 'Value'; evaluated: #value; beEditable; onAcceptEdition: [ :item :newValue | item value: newValue ]; yourself); items: items; open. and then you can edit whatever you want and update your item. Now, since this is a mechanism that has not been used a lot yet in morphic backend, I just discovered and fixed a bug (not in editable tables, but that affects it: https://github.com/pharo-spec/Spec/issues/1263) so if you want to actually use the functionality, you will need to wait until is merged (tomorrow). Esteban On Mar 20 2022, at 10:26 am, Mark O'Donoghue <mark.odonoghue.2010(a)gmail.com> wrote: > Howdy all > > > I am making progress with quite a large application which relies heavily on Spec2 > ( but Spec2 is such a big learning curve for me â especially given the incomplete documentationâ¦ ð) > > I am currently struggling with the following issue: > I have a SpTablePresenter which shows a collection of domain objects (subclassed from Model). > The domain object are instances of âAssetâ which is a relatively simple class. > The table works fine. > > Now, I need to be able to update some columns , but I donât think I want to build a separate form for doing classic CRUD operations. > (There is no need for create or delete functionality â so an in-situ update seems desirableâ¦). > > Iâve made a start using SpStringTableColumn >> beEditable and #onAcceptEdition: > > But I canât see how to work out what row and column has changed, and how I can update the corresponding Asset instance(s). > It thought it would be handled using #whenModelChanged: but there are models in many places (and at several levels in the Spec hierarchy)â¦ > Iâve tried following it all the way down to the adapters and morphs but I canât see how the freshly edited cell interacts with the model or announcements. > > (BTW - It doesnât look like the âselected itemâ features are appropriate since you can do edits in other rows regardless of what row is/isnât selected.) > > Is there a correct and/or elegant way to detect these cell changes in a SpTablePresenter and apply them to my domain objectsâ¦? > > Cheers > Mark > > > > > From: Mark O'Donoghue <mark.odonoghue.2010(a)gmail.com> > Sent: Sunday, 4 July 2021 5:26 PM > To: pharo-users(a)lists.pharo.org > Subject: Question about Spec2 and SpTablePresenter > > > > > > Howdy all > > Iâve got stuck trying to manage Tables â over 12 hours now and Iâm out of ideas!. â¹ > > Any observations / suggestions are most welcomeâ¦ > > Iâve been loading small external files of transactions using NeoCSV into Spec2 tables. > I am trying to use Fuel to persist the table contents so that my application will re-load the working state from where I finished in the last session. > (Iâve opted for Fuel as a simple alternative to having to do the whole object relational mapping thing.) > > The idea is that transactions (and potentially some manual adjustments) will be processed over time. > (This is preferable to having to reload all files from the beginning evert time I run the applicationâ¦) > > The Spec2 tables have been working well until I tried to persist them. > I canât seem to fully re-load them to a previously saved state. > > For example - I can restore the essential contents of my table in most circumstances using: > > restoreObjects > > âfilePresenter1 is a SpTablePresenterâ > > | objects savedEntry | > > objects := CpPersist restoreObjectsFromFileNamed: 'E:\Me\zzzST-Test\demo.fuel'. > > recentFileList := objects at: 1. > currFileFilter := objects at: 2. > savedEntry := objects at: 3. > > self updateFilterButton: currFileFilter. > > filteredFileList := self filterFilesUsing: currFileFilter. > > filePresenter1 items: filteredFileList. > > savedEntry > ifNotNil: [filePresenter1 selectItem: savedEntry ]. > > > However, if any of the table columns are re-sorted , the re-load operation gets confused and I canât get the saved a saved selected item to become selected again. > > (It seems to be confusing the index numbers of the sorted and unsorted lists â even when I match by contents rather than index.) > (I also created an equality test to ensure equivalent entries are recognised by the #= operation in the list of the underlying model ). > > This all works fine - unless I sort a column! > > Since this approach was going to be used on several screens Iâd really like to find a solution. > > Cheers > Mark > Perth, Western Australia

March 20, 2022

Another question about Spec2 and SpTablePresenter

by Mark O'Donoghue

Howdy all I am making progress with quite a large application which relies heavily on Spec2 ( but Spec2 is such a big learning curve for me â especially given the incomplete documentationâ¦ ð) I am currently struggling with the following issue: I have a SpTablePresenter which shows a collection of domain objects (subclassed from Model). The domain object are instances of âAssetâ which is a relatively simple class. The table works fine. Now, I need to be able to update some columns , but I donât think I want to build a separate form for doing classic CRUD operations. (There is no need for create or delete functionality â so an in-situ update seems desirableâ¦). Iâve made a start using SpStringTableColumn >> beEditable and #onAcceptEdition: But I canât see how to work out what row and column has changed, and how I can update the corresponding Asset instance(s). It thought it would be handled using #whenModelChanged: but there are models in many places (and at several levels in the Spec hierarchy)â¦ Iâve tried following it all the way down to the adapters and morphs but I canât see how the freshly edited cell interacts with the model or announcements. (BTW - It doesnât look like the âselected itemâ features are appropriate since you can do edits in other rows regardless of what row is/isnât selected.) Is there a correct and/or elegant way to detect these cell changes in a SpTablePresenter and apply them to my domain objectsâ¦? Cheers Mark From: Mark O'Donoghue <mark.odonoghue.2010(a)gmail.com> Sent: Sunday, 4 July 2021 5:26 PM To: pharo-users(a)lists.pharo.org Subject: Question about Spec2 and SpTablePresenter Howdy all Iâve got stuck trying to manage Tables â over 12 hours now and Iâm out of ideas!. â¹ Any observations / suggestions are most welcomeâ¦ Iâve been loading small external files of transactions using NeoCSV into Spec2 tables. I am trying to use Fuel to persist the table contents so that my application will re-load the working state from where I finished in the last session. (Iâve opted for Fuel as a simple alternative to having to do the whole object relational mapping thing.) The idea is that transactions (and potentially some manual adjustments) will be processed over time. (This is preferable to having to reload all files from the beginning evert time I run the applicationâ¦) The Spec2 tables have been working well until I tried to persist them. I canât seem to fully re-load them to a previously saved state. For example - I can restore the essential contents of my table in most circumstances using: restoreObjects âfilePresenter1 is a SpTablePresenterâ | objects savedEntry | objects := CpPersist restoreObjectsFromFileNamed: 'E:\Me\zzzST-Test\demo.fuel'. recentFileList := objects at: 1. currFileFilter := objects at: 2. savedEntry := objects at: 3. self updateFilterButton: currFileFilter. filteredFileList := self filterFilesUsing: currFileFilter. filePresenter1 items: filteredFileList. savedEntry ifNotNil: [filePresenter1 selectItem: savedEntry ]. However, if any of the table columns are re-sorted , the re-load operation gets confused and I canât get the saved a saved selected item to become selected again. (It seems to be confusing the index numbers of the sorted and unsorted lists â even when I match by contents rather than index.) (I also created an equality test to ensure equivalent entries are recognised by the #= operation in the list of the underlying model ). This all works fine - unless I sort a column! Since this approach was going to be used on several screens Iâd really like to find a solution. Cheers Mark Perth, Western Australia

March 20, 2022

Re: Null Object Pattern

by Richard O'Keefe

An override of #doesNotUnderstand: *is* (an instance of) the problem. What part of "you may think you know what to forward now, but just wait a couple of months or install an additional package and there will be *more* selectors you needed to think about but didn't" is hard to understand? Proxies done right are proxies *relative to a specified protocol*. Let me give you a personal example. I wanted something that was like an OrderedCollection but could only hold elements of a specific class. No worries, just make a proxy. Make a bare-bones object, define all the #add... methods to check their argument, and use #doesNotUnderstand to forward everything else to the underlying OrderedCollection. The first problem is the selectors that the bare-bones object *does* understand by virtue of being an object. (Remember there are *hundreds* of these selectors in Squeak, Pharo, VisualWorks, even in gst there are more than 120). You must, for example, ensure that #instVarAt: is forwarded, not handled locally, BUT you must also ensure that #instVarAt:put: is handled locally, not forwarded. And then one day you find that your program has broken, because mutable collections now have aMutableCollection inPlaceCollect: collectBlock and that can put unacceptable results in the collection *without* going through any #add... method. Eventually you realise "handing out a wrapper for this collection constrained to only allow adding certain things" is the wrong way to do it, and you do something like constrainedAdder: constraint ^[:x | (constraint value: x) ifTrue: [self add: x] ifFalse: [DomainError receiver: self selector: #add:]] or you do something else entirely, like handing out a wrapper with a *narrow* interface that doesn't make the slightest pretence of *being* the other object. I *could* make a batch of ricin and store it in my granddaughter's bedroom, but I'm not going to. I *could* make a proxy by going through #doesNotUnderstand: but I am not going to. That would be a textbook example of maxim 38: "Just because it's easy for you doesn't mean it can't be hard on your clients." On Sun, 20 Mar 2022 at 15:18, James Foster <smalltalk(a)jgfoster.net> wrote: > I donât understand. Wouldnât an override of #'doesNotUnderstand:â solve > this problem? The proxies Iâve seen subclass from nil or ProtoObject and > forward almost everything to the target. Itâs really very easy. > > On Mar 19, 2022, at 3:14 AM, Richard O'Keefe <raoknz(a)gmail.com> wrote: > > An object should be a Proxy or Stub only with reference to a specific > protocol, which should be kept narrow. > > Being a Proxy is a form of coupling. Proxying a wide > interface creates maintenance problems: > Squeak 5.3 : Object selectors size => 485 > Pharo 9.0 : Object selectors size => 435 > astc : Object selectors size => 325 > VW 8.3PUL : Object selectors size => 304 > > The interface of Object is HUGE. You want to bet that > your Proxy got *all* of the methods right? This > interface didn't get that way all at once; it grew. > The number was 78 in Smalltalk-80. At a minimum, then, > Smalltalk systems have accreted one extra Object method > every two months. > > So you set up your proxy to *flawlesly* mirror Object, > and then, WHOOPS, upgrade Smalltalk and now there is a > method that Object has and your Proxy either lacks (if > it descends from ProtoObject but not Object) or inherits > an inappropriate version of (if it descends from Object). > > What this means is that nobody ever *does* flawlessly > mock everything in the public interface of an object > they are Proxying. They proxy a *limited* protocol. > Because that is all they *can* do. > > Look, I know that people who have been trained to work > with the stuff can use C4 as cooking fuel. But I haven't > had that training, so I won't touch the stuff. In the > same way, I dare say there are things *you* can safely > do in Smalltalk that fumblefingers here would be burnt > badly by. There are many things that *can* be done that > I *won't* do. In a chemistry lab, I would not work with > ClF3 let alone O2F2. In Smalltalk, I don't monkey with > #isNil. > > On Fri, 18 Mar 2022 at 03:52, James Foster <smalltalk(a)jgfoster.net> wrote: > >> Richard, >> >> I very much admire Dijkstraâs admonition regarding âThe Humble >> Programmerâ and was pointing a student to that article just this week. >> >> In any case, I think youâve demonstrated that you now comprehend the >> argument against inliningâyou just donât agree. Thatâs fair and I think the >> discussion has been clarified. Would it be fair to say that you have an >> âideological objectionâ to allowing a Proxy or Stub to transparently stand >> in for another object (say, in a two-object-space environment such as Pharo >> and GemStone)? That is, a domain object canât be replaced by a Proxy or >> Stub without a wholesale rewrite of the rest of the application? I respect >> that as a reasonable position (demanding perfect clarity), but I see a cost >> to that position as well. >> >> Of course, if you really want to avoid allowing the receiver to chose its >> response to a message, you can use other messages. So if you want to find >> out if an object is identical to nil you should use `nil == myObject` to >> ensure that there was not an override of #âisNilâ or #â==â by the objectâs >> class. >> >> James >> >> On Mar 17, 2022, at 2:27 AM, Richard O'Keefe <raoknz(a)gmail.com> wrote: >> >> My chief concern is that I am a bear of very little brain, >> and if you change the meaning of #isNil to anything at all >> other than "is the receiver identical to nil" you *WILL* >> (not may) confuse me. This extends to things that happen >> not to be inlined: if even a god-like Smalltalker like >> Andres Valloud overloads #, to something other than "combine >> the collection that is the receiver with the collection that >> is the argument to yield a new collection" than I *WILL* >> most certainly be confused and find the code unmaintainable. >> Smalltalk being Smalltalk, if you admit an inconsistent >> overload anywhere, I can no longer understand sends of that >> selector anywhere. One of the things to like about Traits >> is that you can say "this class doesn't just *happen* to >> have selectors x and y, it has them *because* it has this >> whole consistent bundle of selectors." >> >> There are more annotations documented for my Smalltalk >> compiler than are actually implemented. One that *is* >> implemented is <doNotOverride>, and it has caught more >> mistakes than I care to admit to. It's particularly >> important for a bundle of methods with varying arguments >> that are meant to be routed through a single method, >> which *is* meant to be overridden. It makes sure that >> I override the *right* method. (Take #= and #~= as an >> obvious example.) >> >> Once you start down the path of lying about things like #isNil >> you find that EITHER you have to go very far down that path >> and override #== and #instVarAt: and a whole lot of other >> things OR you are working with a semantically incoherent system. >> >> "How should a proxy (https://en.wikipedia.org/wiki/Proxy_pattern) to nil >> respond to the #âisNilâ message?" >> >> It SHOULD NOT LIE. A proxy *isn't* nil, and it doesn't *behave* like nil, >> even if it is a proxy for nil. A proxy, qua proxy, can do things that nil >> cannot. Use another selector, #isEffectivelyNil, or whatever reveals your >> intentions, and give it what semantics you find useful. >> >> "How should the Null Object Pattern ( >> https://en.wikipedia.org/wiki/Null_object_pattern) respond to #âisNilâ?" >> >> It should answer false. Period. No ifs, buts, quibbles, or maybes. >> The whole *point* of the Null Object Pattern is to return something >> that *isn't* nil, that has quite a different protocol. If you call >> something that is supposed to return either a Foo or a NullFoo, and >> it gives you nil instead, there is a BUG in what you just called so >> the sooner you find out the better. What you want is >> >> Foo >> isNullFoo ^false >> NullFoo >> isNullFoo ^true >> and no other class defines #isNullFoo. >> >> That way, when you ask "tripeWorks grobblingMill lastPallet isNullPallet" >> (a) you make it clear to someone reading your code what you are expecting >> (b) if you DON'T get what you are expecting, Smalltalk will tell you. >> >> I must admit that on the few occasions when I've used Null Object >> I've used an all-purpose #isMissing instead of a task-appropriate >> #isNullFoo, but then I figured out what I was doing wrong. You >> look at the code, you say "there's *something* off here, but I don't >> know what." But when you ask "what, exactly, does this method MEAN?" >> you realise "oh, THAT'S what I was doing wrong." #isMissing told me >> it was a NullPerson or a NullAddress or a NullPartsList or ... but >> in this case I needed to know whether it was a NullSummary. >> >> And of course you run into E.F.Codd's lesson: "one NULL is never >> enough, information can be missing for more than one reason". >> Take the familiar example of a phone number: >> - I know that Fred's phone number is X >> - I know that Fred has a phone but I don't know what the number is >> - I don't know whether Fred has a phone or not >> - I know that Fred has no phone >> There's room for three *different* null objects there. >> Should we have UnknownNumberOfActualPhone to answer false to #isnil >> and NonNumberOfNonexistentPhone to answer true? Or what? >> >> By the way, you may have misunderstood my benchmark. >> It wasn't that #isNil or even _ ifNotNil: speeded up by >> 10%, it was the *whole* matrix-munching benchmark that >> speeded up. Certainly not a big deal, but it's not >> something I'd be happy to give up in order to get less >> maintainable code. >> >> >> >> >> >> >> >> >> On Thu, 17 Mar 2022 at 18:21, James Foster <smalltalk(a)jgfoster.net> >> wrote: >> >>> Richard, >>> >>> My _concern_ with inlining is that since it is designed to short-circuit >>> dynamic method lookup, it is impossible to call a _different_ >>> implementation. That is, you lose the opportunity to have the _receiver_ >>> decide how to respond to the message. You may think of it as a message, but >>> the caller is deciding how the receiver will respondâwhich largely defeats >>> the purpose and role of it being a message. Yes, at the machine code level >>> you are performing a branch instruction, but when comparing OOP to >>> Procedural Programming we typically make a distinction between âmessagesâ >>> and "procedure calls." The distinction is that the receiver gets to decide >>> how to respond to a message. In C++ this is the distinction between a >>> âvirtual" and "non-virtual" function. By inlining, you are converting the >>> function from a virtual function to a non-virtual function, and this can >>> make a difference (which is why virtual functions exist). >>> >>> How should a proxy (https://en.wikipedia.org/wiki/Proxy_pattern) to nil >>> respond to the #âisNilâ message? How should the Null Object Pattern ( >>> https://en.wikipedia.org/wiki/Null_object_pattern) respond to #âisNilâ? >>> >>> And, yes, Iâm sure you can come up with benchmarks that show a >>> measurable difference, but what is the impact in realistic code? When >>> someone asked about inlining #âyourselfâ in GemStone I believe I measured >>> the performance as taking 2 nanoseconds per call (on a 2012 machine). A 10% >>> speedup would make it 1.8 nanoseconds. Is that worth it? Maybe, maybe not. >>> >>> Note that I described my position as a âconcern,â not an ideological >>> objection. Mostly Iâm giving a rationale for something that doesnât seem to >>> be explained very well for you. I accept that there may be a time for >>> inlining, but I can âcomprehend" another side to the issue. >>> >>> James >>> >>> On Mar 16, 2022, at 9:42 PM, Richard O'Keefe <raoknz(a)gmail.com> wrote: >>> >>> We're still not on the same page. >>> You seem to have some ideological objection to inlining that >>> I am completely failing to comprehend. >>> Just because a procedure call (message send) is inlined doesn't >>> in the least mean it *isn't* a procedure call (message send), >>> just as compiling a procedure call (message send) as a jump >>> (last-call optimisation) doesn't mean it *isn't* a procedure >>> call (message send). >>> By the way, forget about "40 years ago". >>> I just did an experiment in Pharo 9, and found that >>> using "_ ifNotNil: " instead of "_ izNil ifFalse: " >>> -- where izNil is a non-inlined self == nil -- >>> gave a 10% speedup, in a test code where real work was going >>> on as well. >>> As for turning off all inlining, what do you think that would >>> do to #ifFalse:ifTrue: and its relatives? >>> >>> >>> On Thu, 17 Mar 2022 at 08:34, <sean(a)clipperadams.com> wrote: >>> >>>> >>>> To start with, why do you CARE whether a particular method is inlined >>>> or not? >>>> >>>> I care because it makes âeverything is a messageâ a lie! And I suspect >>>> (no proof and could be wrong) itâs an optimization that only made sense >>>> with the hardware constraints of 40+ years ago. Arguing against premature >>>> optimization is hardly something I just made up ;-) >>>> >>>> This makes absolutely no sense to me. What makes you think that the >>>> combination "_ isNil ifFalse: [_]" will NOT be inlined? >>>> >>>> I may have been unclear. My intent was to communicate: âIâd like to >>>> stop ALL* inlining of messages by default if possibleâ >>>> >>>> *or as many as practical >>>> >>>> The thing that rings loud alarm bells for me is there being "long >>>> chains" in the first place. >>>> >>>> I agree that it is in general a smell, but long chains was tangential >>>> to the intention above >>>> >>>> Can you give an example? >>>> >>>> I donât know if I can think of one thatâs not contrivedâ¦ Wrapping >>>> something external? Squeakâs AppleScript support used to mirror the >>>> underlying AS, which is pretty much exactly that. >>>> >>>> In my own programming, I've generally found that nils turning up in the >>>> middle of a chain indicates a serious design error somewhere. >>>> >>>> Agreed. See smell comment above. >>>> >>> >>> >> >

March 20, 2022