[Cuis] [Philosophy] Do we need pool dictionaries?

[Juan Vuletich]

On 22/01/2014 03:39 p.m., Nicolas Cellier wrote:
>
> 2014/1/22 Sean P. DeNigris <sean at clipperadams.com 
> <mailto:sean at clipperadams.com>>
>
>     Juan Vuletich-4 wrote
>     > I don't like pooldictionaries. They look like "hidden globals"
>     to me,
>     > and they are as bad as regular globals. Maybe there were good
>     reasons
>     > for them 30 years ago, but I don't see any today, except for
>     > compatibility.
>
>     I agree that they should be avoided if possible, but they seem
>     useful e.g.
>     for NativeBoost in Pharo. There are many C constants, and you'd
>     like to
>     refer to them directly so you can copy/paste from documentation,
>     and so that
>     you don't have to context switch as much when writing C calls.
>     With shared
>     pools, you can import them into the namespace of all classes that
>     directly
>     access the library.
>
>
> But then, what difference with class variables?
> class vars also are  global, just with a bit more restrictive 
> visibility (subclasses)...
>
> Usage of such globals for well known constants (like a C macro) is not 
> that problematic.
> Of course, it's possible to replace such shared pool by message send:
> Character cr rather than CR.
> But note that you replace a global (CR) by another global (Character).
> OK reducing the number of globals is already something...
> Also, motherness is not always that trivial, is it Text centered or 
> TextAttribute centered?
>
> Sure, some small optimization difference still exist:
> - is a new instance created or a constant shared?
> - is a message sent or not (note that Squeak 4.5 now send a message to 
> access the #value of a global)
> That indeed might have influenced decisions in the 70s.
>
> Usage as a shared mutable state is more problematic
> It's hardly possible to avoid such states (like a registry of opened 
> files for example)
> in this case, yes, it's better to restrict access (encapsulate) with a 
> class var.
> But I think Pharo already cleaned out the ugliest examples in 
> TextConstants, no?

Cuis (this is what this list is about) makes no use of pool 
dictionaries. But they are there in case someone needs or wants them. 
Cuis is a Smalltalk-80 system. Removing support for pool dictionaries 
would mean turning Cuis into a "Smalltalk inspired" kind of system.

Cheers,
Juan Vuletich
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