ah ok my bad, I learned something new, thank you. Is it possible to embed this method to a new class ? lets say i like what i did in workspace and send it directly to a new class.
On Sat, Dec 14, 2013 at 5:15 PM, Norbert Hartl <[email protected]> wrote: > > Am 14.12.2013 um 15:58 schrieb kilon alios <[email protected]>: > > yes sorry i meant global variables , the ones you define in workspace like > a := 1. > > Those aren’t globals. Everything you do in the workspace is compiled as > method (UndefinedObect>>#DoIt) and executed. There are only a handful of > global values and there is the smalltalk dictionary where names can be > looked up. > > Norbert > > > On Sat, Dec 14, 2013 at 4:30 PM, Norbert Hartl <[email protected]> wrote: > >> >> Am 14.12.2013 um 12:09 schrieb kilon alios <[email protected]>: >> >> why we need globals anyway ? why not use classes instead ? >> >> >> Class names are globals. A class is registered in a global namespace by >> its name. Names need to be looked up. How should it work in another way? >> >> Norbert >> >> The only use I see of globals is in workspace and I am sure we could find >> a way to automate or make the creation of classes faster inside workspace >> instead of using globals. Since OO is the very foundation of Pharo I don't >> see why one would need globals anyway. If that forces us to make object >> more flexible so be it. Way better than creating concepts that works with >> this tools and not work with the other tool or could work if you do this >> and that , ending up making things more complex than they need to be. >> >> I think it would make even the transition from workspace to browser >> easier, or even completely replace workspace with the browser. >> >> I always found workspace unnecessary anyway. >> >> >> On Sat, Dec 14, 2013 at 12:47 PM, Norbert Hartl <[email protected]>wrote: >> >>> >>> >>> > Am 14.12.2013 um 05:41 schrieb Igor Stasenko <[email protected]>: >>> > >>> > >>> > As you may know, smalltalk global dictionary contain all symbols >>> defined globally, >>> > so you can access them directly in any piece of code i.e. when you >>> write: >>> > >>> > Object new >>> > >>> > it actually means 'send message #new to object, associated with >>> #Object name in globals dictionary. >>> > >>> > Most of globals are classes, but some of them , like Transcript, >>> World, Display etc are not. >>> > And i was always thinking there's something wrong with these globals >>> (actually there's multiple 'wrongs'), but finally, i think i can answer >>> myself, what is most basic wrong with them: they miss any form of >>> declaration. >>> > >>> > Most of variables in smalltalk require declaration, such as temps, >>> method arguments, instance variables , class variables, pool variables, >>> > but not globals. >>> > Even classes, from formal point of view do not require declaration, >>> > because actually the usual: >>> > >>> > Object subclass: #Collection >>> > instanceVariableNames: '' >>> > classVariableNames: 'MutexForPicking RandomForPicking' >>> > poolDictionaries: '' >>> > category: 'Collections-Abstract' >>> > >>> > is _definition_ but not declaration: >>> > >>> > Collection definition => >>> > >>> > 'Object subclass: #Collection >>> > instanceVariableNames: '''' >>> > classVariableNames: ''MutexForPicking RandomForPicking'' >>> > poolDictionaries: '''' >>> > category: ''Collections-Abstract''' >>> > >>> > in fact, it is just a message sent to 'Object' variable (at some >>> moment in the past) , and there's nothing >>> > in language which enforces the rule that evaluating such expression >>> must declare new global, named Collection, except from environment we're >>> working in. >>> > >>> > The absence of declaration for globals leads to following problems: >>> > since declaration point is not defined, all tools (including compiler) >>> assume that given name always been there, and always accessible. Which >>> leads to bootstrap problems. >>> > There's no way to determine if given piece of code (which uses some >>> global) will keep functioning properly, once you unload certain package. No >>> way to determine dependencies (and as consequence the order of code loading >>> during bootstrapping). >>> > Also, it is hard to determine, to which package certain global >>> belongs. While it is easy to tell for classes since they having category, >>> for globals like Transcript, Display etc, there's no way to tell anything. >>> > Piece of cake, you can say: since Display is instance of >>> DisplayScreen class, then such variable must belong to same package as >>> DisplayScreen, right? >>> > Wrong! >>> > Just for example, imagine i create variable named >>> MyWindowMousePosition, which will contain an instance of Point. Does it >>> means that such variable should belong to same package as Point class? I >>> guess not. >>> > >>> > So, to sum up, i think we should really think how to introduce a way >>> to declare globals in package-based ecosystem, where each global belongs to >>> certain package, and then since packages form dependency hierarchy, you can >>> easily detect whether you allowed to use certain global in given context or >>> not, >>> > to prevent forming dependency loops. >>> > But even if we will weaken contract and allow having dependency loops, >>> even in such case declarations can help us to clearly tell which pieces of >>> code will stop functioning properly, if package which declares given >>> variable are not present in system. >>> > >>> > The last aspect of bootstrapping problem is order of initialization, >>> > because declaring variable doesn't means you can use it right away, >>> > since it may be not properly initialized yet (otherwise we will be >>> forced to always use lazy initialization pattern). >>> > >>> > From this perspective, IMO package should not only have unordered list >>> of classes/symbols it declares/defines, but also contain information in >>> which order they must be initialized while loaded. >>> > From other side, i don't really like introducing too much formalism >>> and rules, and keep them as minimal as possible, following smalltalk spirit. >>> > >>> > What you think? >>> >>> I think packages should be first class citizens. A package once loaded >>> provides an environment/namespace/... that declares all the (exported) >>> symbols that should be accesible global. The smalltalk dictionary should >>> rather be a list of those namespaces/environments/... A package should also >>> have an initialize method where you could specify order of class >>> initialization if necessary ( and other things). Furthermore I would like >>> to see class initializers idempotent. So when loading a package the package >>> initialize is invoked first and then the class initializers, As they are >>> idempotent a possible double invocation is not a problem. >>> Dependencies are always hard. I would start thinking about metacello >>> defining all the possible dependencies regarding platforms, platform >>> versions etc. At load time there is only one dependency graph and that >>> could be reflected by the system. And this graph is not dependent on the >>> tool that loaded the code. >>> With this in place unloading should be rather easy. Dependencies can >>> warn the user about an harmful action and when the namespace is removed all >>> global definitions are automaticall removed. >>> >>> That is what I think. But I also think that there should be a >>> possibility to load something that doesn't end being global. A way to load >>> a package that isn't added to the global namespace (smalltalk dictionary) >>> but to a package namespace would also be very good. Not everything needs to >>> global but we can only load global things. That is a flaw in my opinion. >>> And it prevents cool things like loading multiple versions of a code in >>> separate packages. >>> >>> Norbert >>> >> >> >> > >
