On 21 December 2010 23:21, Charles Monteiro <charles@nycsmalltalk.org> wrote:

the first I heard of traits was indeed I believe from a paper by Stef's group if I recall correctly. So that's exactly what I mean.

Nested classes are an organizational and a "structural" construct.

A nested class is defined from within an outer class. They are used when a class is only likely to be instantiated (used) from within another class. For example (just an example) , when you instantiate aBody you would want to instantiate two legs but two legs outside the context of a body may not make sense.

So that seems of some value.

Frankly, nested classes/namespaces is userful to limit the scope of names.

From organizational/structural point of view it not so valuable. Because there is enough ways in smalltalk how to organize your model nicely without using extra dimension(s), such as nested classes.

You can also used it to simply group classes i.e. an outer class Drawing, may specify inner classes Line, Circle, Rectangle etc. To instantiate an inner class you need special access syntax in Ruby you would do something like this:

aCircle = Drawing::Circle.new

ok, that's alright if I'm using nested classes to group.

but you can also do this:

aLeg = Body::Leg.new

you can just do: Body Leg new. and in Body>>#Leg answer any class you want to play role as 'Leg'. Or you missing double colons in the middle? :)

but wait I thought you it only made sense to instantiate a Leg from within the context of a body.

Anyhow, I sort of have mixed feelings about it i.e. if they are worth the extra overhead. Not to mention that Smalltalk's IDE's are not setup to handle them. File based IDE's of course don't care, they just care about the source representation.

This 'nested classes' to me look like nested namespace(s), and nothing more. I'd rather introduce namespaces in smalltalk rather than nested classes. But while having a long background of languages which having namespaces, i could not say that i miss them in smalltalk too much. I can group classes using categories, and that is enough from human perception perspective. Limiting the visibility scope and playing all that 'public/private' games - this is an overengineering. My 2c -- Best regards, Igor Stasenko AKA sig.

On 22 December 2010 00:24, Charles Monteiro <charles@nycsmalltalk.org> wrote:

Igor:

Let me preface that I pay my bills doing VisualWorks by day and we have namespaces.

Yeah, I'm not sold on them but several languages have them and so I wondered what I was missing. In a way if you could use them to constraint the instantiation of a nested class to only occur within a outer class it may have some merit i.e. an arm can only exist in the context of a body etc, but how value does it add ? From my perspective traits adds value and its worth its cognitive overhead, not sold on nested classes.

me neither

"you can just do: Body Leg new.

and in Body>>#Leg answer any class you want to play role as 'Leg'.

Or you missing double colons in the middle? :) "

I missed something here ? , in Ruby the syntax is:

Body::Leg.new

sorry, i was imprecise. I meant to say 'do you miss the colons?'.. (sarcasm) :)

I guess you are saying that in Smalltalk I can just setup the accessors to return whatever plays the role of a Leg but part of the point is that the Leg class is defined within a Body class and I guess if you are looking a source file in Ruby that might be helpful :)

i.e.

class Body

   class Leg

       def method1

       end

  end

end

The fact that Ruby and other language developers are not used to browser categories maybe makes this helpful in some way.

I don't think so. You can't create a class in smalltalk without assigning a category to it, so, a developer, who just started with smalltalk, are forced to use categories anyways. Yes, and the fact that nested classes systax like in Ruby or other languages are possible, because they using a 'source files' , which is single bloat of code. While in smalltalk, you usually operating with single method at one moment of time, and all browser operations and UI are optimized around that simple idea, so you don't need to scroll endless file with source code to find the method or nested class you are looking for at line #10974.

-- View this message in context: http://forum.world.st/Nested-classes-tp3125667p3159885.html Sent from the Pharo Smalltalk Users mailing list archive at Nabble.com.

-- Best regards, Igor Stasenko AKA sig.

Hi, Am 21.12.2010 um 22:45 schrieb Mariano Martinez Peck <marianopeck@gmail.com>:

just by ignorance.....weren't traits invented in smalltalk?

no; Self had them in the Nineties, and they were there before that. The journal version of the ST traits paper has all the references. Best, Michael

thanks, Eliot had mentioned Newspeak quite a while back ago, it seems that its progressing a bit, installing it now. -- View this message in context: http://forum.world.st/Nested-classes-tp3125667p3159951.html Sent from the Pharo Smalltalk Users mailing list archive at Nabble.com.

yes, answer is ok. Indeed , namespaces in VW are about name collision nothing more. It just looks nicer :). I hope I will have the cash and time to go fly to Europe, the dollar is not so good lately :) and have a more in depth discussion of this. So go give birth, I will await the child. -Charles -- View this message in context: http://forum.world.st/Nested-classes-tp3125667p3160624.html Sent from the Pharo Smalltalk Users mailing list archive at Nabble.com.