[Pharo-project] Pharo and Namespaces

Stéphane Ducasse stephane.ducasse at inria.fr
Wed Jun 27 11:27:11 EDT 2012


On Jun 27, 2012, at 4:44 PM, James Foster wrote:

> Stef,
> 
> I'm sorry to hear about your burnout and I understand that you are not prepared to seriously discuss the issues that others have raised. I hope when the issue is raised again (it does seem to come up every year or so!) we can correct some of the misunderstandings that exist.

yes we are discussing regularly that topic and Camille is writing a master where all the points are discussed and summarized with pros and cons.
Now for 20 we should finish all the open tracks we have.

Stef

> 
> Best wishes,
> 
> James
> 
> On Jun 27, 2012, at 12:08 AM, Stéphane Ducasse wrote:
> 
>> James 
>> 
>> sorry but I'm at home stopped for 10 days because of a burnout (linked partly to pharo and the business I want to spawn for the community).
>> We talked endlessly about namespaces and so far we lived happily without. Right now I will not talk about that. Read subsystem the paper of wirfs-brock
>> if you want to see what I would prefer to have. But we need to have a scientific approach to evaluate.
>> And yes I read the implementation two years ago.
>> Finally did you see the list of topics that I mention? 
>> 	- do you want to help in any of them to make pharo better?
>> 	because we have to get them first and I need all my energy for them.
>> 
>> Stef
>> 
>> 
>> On Jun 27, 2012, at 12:25 AM, James Foster wrote:
>> 
>>> On Jun 26, 2012, at 12:51 PM, Stéphane Ducasse wrote:
>>> 
>>>> On Jun 26, 2012, at 9:30 PM, James Foster wrote:
>>>> 
>>>>> On Jun 26, 2012, at 11:19 AM, Stéphane Ducasse wrote:
>>>>> 
>>>>>>>>> What happened to the project from Germán Leiva
>>>>>>>>> http://www.youtube.com/watch?v=n4I7fSVNX2A
>>>>>>>> 
>>>>>>>> we do not want class level namespace because this is the mess
>>>>>>> 
>>>>>>> As the sponsor for Germán's project, I have some interest in this topic. Stéphane has said a couple times that it is wrong but has never taken time to explain his objections.
>>>>>> 
>>>>>> We do not want to have class name resolution at the granularity of a class.
>>>>> 
>>>>> And are you saying this because you think Germán's implementation does this?
>>>>> 
>>>>>> Why because it means that in the same package reading the code containing a class Foo could be a different one.
>>>> 
>>>>>> Why because it means that in the same package, reading the code containing a class Foo could be a different one.
>>>> 									  ^^^^^
>>>> 
>>>> Class level namespace import means that in a given class, a method accessing the variable Foo may end up pointing to another class Foo in a class in the same package importing another namespace. 
>>> 
>>> I still don't understand the definition. What do you mean by "another class Foo in a class." How can a class be in a class? Is Foo defined in two packages? Is the method on the class Foo? Should the name be resolved to the Foo in the package containing the method or to another Foo? Perhaps it would help if you named the sample classes, packages, and methods.
>>> 
>>> Are you saying that if the namespace is allowed to be defined (or refined) at any level other than the package, then it is lumped into the bucket called "class level namespace import"?
>>> 
>>>>> I don't understand your example. I don't know what you mean by "package reading the code." Are you describing a package that defines classes Foo and Bar, and a method in a class Bar that references the Foo in the same package? Are you providing this example because you think Germán's implementation does not support this use case?
>>>> 
>>>> No 
>>>> I just say that changing binding of variables at the class level is not a good granularity. I do not want to have 
>>>> 
>>>> Object subclass: #NameOfSubclass
>>>> 	instanceVariableNames: ''
>>>> 	classVariableNames: ''
>>>> 	poolDictionaries: ''
>>>> 	category: 'Bob'
>>>>>>> 	environment: 
>>> 
>>> Is it your impression that Germán's implementation requires this? If so, on what do you base that understanding? Have you looked at the code? 
>>> 
>>>>>> I'm saying that since years.
>>>>> 
>>>>> I agree you have been saying that Germán's implementation isn't what you want. I just don't understand what you don't like about it.
>>>> 
>>>> because this is a class level import.
>>> 
>>> I still don't know what you mean by "class level import" or why you think Germán's implementation fits your definition. 
>>> 
>>>>> Name resolution of all variables (including Globals, of which Classes are a subset) should be part of a method compile. At the time a method is compiled, an 'environment' should be provided to the compiler that indicates how global name resolution should occur.
>>>> 
>>>> Usually this is the class of the method.
>>> 
>>> By "Usually" do you mean in pre-namespace Pharo? That is, the class is one of the factors that the compiler considers in doing name lookup? Is the "usual" approach good? Would it still be a factor considered by the compiler in an environment namespace regime?
>>> 
>>>>> This is a tools issue and it should be possible to specify the default namespace environment for the method, for a method category, for a class, for a class category, for a package, and for the system as a whole.
>>>> 
>>>> no this is a question of language design.
>>> 
>>> Do you consider packages to be part of the language? I have always thought that one of the nice things about Smalltalk is how little of the development environment is actually part of the language. Being able to augment things through tools rather than changing the language seems to me to be a feature, not a bug. 
>>> 
>>>>> In addition, within a particular method it should be possible to explicitly reference a particular namespace environment, whether through syntax (dot or double colons)
>>>> 
>>>> No we do not want to have that.
>>>> We want import to be specified at the border: i.e. during module import. Inside a module the world is flat and as a developer I do not want to know that this Point is from Core when that one is from MyCore.
>>> 
>>> By "I do not want to know" do you mean "I do not want to be required to specify" or do you mean "I do not want anyone else to be able to find out"? If I want to know (say, to build tools), would that be okay? If I'm willing to let you remain ignorant of a global's source would you be willing to let me be enlightened?
>>> 
>>>> If I want both, at the module import level I write
>>>> 
>>>> 	Import: Point from: core as: CorePoint; 
>>>> 	import: Point from: dev as: DevPoint;
>>> 
>>> What object implements #'import:from:as:'?
>>> 
>>>>> or through message sends (e.g., a Dictionary's #'at:' method). I prefer not to add new syntax and favor GemStone's implementation over that of VisualWorks.
>>>> 
>>>> I dislike them both.
>>>> A module should provide a certain level of encapsulation, else naming convention is good enough. 
>>>> Because else having namespace does not prevent you to have to declare that WA is not a namespace somebody else should use. 
>>> 
>>> You say that you "do not want to" allow code "to explicitly reference a particular namespace." Do you mean that arbitrary code should not be able to see a global that is not explicitly imported at package load time and that code should never be able to explicitly look at and manipulate namespaces. Really? This seems to me to be very much contrary to the existing spirit of reflection and introspection in Smalltalk and would make tools much more limited. I suspect that this is not really what you mean.
>>> 
>>> I believe that a package should be allowed to provide a default environment, but I don't see the need to make it mandatory or exclusive. I believe that a class should be allowed to override the default environment, but I don't think it should be required. 
>>> 
>>> If a class is allowed (but not required) to override the default (provided by the package/module, for example), does that make it a "class level import" (and wrong, in your view)?
>>> 
>>> What I understand from your statements so far is that Germán's approach allows too much flexibility (namespace can be specified not just at the package level but also at the class level and explicitly in code). You do not want to allow anyone to experiment with different levels of granularity. Is that it?
>>> 
>>> Thanks for engaging in the discussion.
>>> 
>>> James Foster
>>> 
>>> 
>> 
>> 
>> 
> 
> 





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