Re: [Pharo-dev] Tricky Metaclass>>binding

[Denis Kudriashov]

Yes

13 сент. 2017 г. 18:59 пользователь "Stephane Ducasse" <
stepharo.s...@gmail.com> написал:

> I imagine that you imply keeping the cGlobalVariable binding for the
> real global variable.
>
> On Wed, Sep 13, 2017 at 4:52 PM, Denis Kudriashov 
> wrote:
> > So after discussion the solution would be:
> > - ClassBinding for instance side method literals and globals dictionary
> > (instead of GlobalVariable)
> > - MetaclassBinding for the last literal of class side methods. It will
> > include proper comment about where it is used and how, with description
> of
> > current trick
> >
> > 2017-09-13 16:45 GMT+02:00 Marcus Denker :
> >>
> >>
> >> > On 12 Sep 2017, at 17:33, Guillermo Polito  >
> >> > wrote:
> >> >
> >> > I don't know... I found the idea of having a Metaclass binding
> >> > strange...
> >> >
> >> > I mean,
> >> > - metaclasses are not stored in any name dictionary such as Smalltalk
> >> > - nobody references them directly in source code but by their direct
> >> > classes
> >> >
> >> > The metaclass binding is there just for one thing really: methods need
> >> > an association to know their class in case they have to do a super
> send. And
> >> > transitively this is a compiler problem also. But anybody else
> accesses
> >> > metaclasses' bindings.
> >> >
> >> yes, we need it just for the last literal.
> >>
> >> We added the “if there is a method, get the binding from there” we adde
> as
> >> else
> >> we would compiler every class side method with a new Association
> instance,
> >> which
> >> wastes lots of space.
> >>
> >> Marcus
> >
> >
>
>

Re: [Pharo-dev] Tricky Metaclass>>binding

[Stephane Ducasse]

I imagine that you imply keeping the cGlobalVariable binding for the
real global variable.

On Wed, Sep 13, 2017 at 4:52 PM, Denis Kudriashov  wrote:
> So after discussion the solution would be:
> - ClassBinding for instance side method literals and globals dictionary
> (instead of GlobalVariable)
> - MetaclassBinding for the last literal of class side methods. It will
> include proper comment about where it is used and how, with description of
> current trick
>
> 2017-09-13 16:45 GMT+02:00 Marcus Denker :
>>
>>
>> > On 12 Sep 2017, at 17:33, Guillermo Polito 
>> > wrote:
>> >
>> > I don't know... I found the idea of having a Metaclass binding
>> > strange...
>> >
>> > I mean,
>> > - metaclasses are not stored in any name dictionary such as Smalltalk
>> > - nobody references them directly in source code but by their direct
>> > classes
>> >
>> > The metaclass binding is there just for one thing really: methods need
>> > an association to know their class in case they have to do a super send. 
>> > And
>> > transitively this is a compiler problem also. But anybody else accesses
>> > metaclasses' bindings.
>> >
>> yes, we need it just for the last literal.
>>
>> We added the “if there is a method, get the binding from there” we adde as
>> else
>> we would compiler every class side method with a new Association instance,
>> which
>> wastes lots of space.
>>
>> Marcus
>
>

Re: [Pharo-dev] Tricky Metaclass>>binding

[Denis Kudriashov]

So after discussion the solution would be:
- ClassBinding for instance side method literals and globals dictionary
(instead of GlobalVariable)
- MetaclassBinding for the last literal of class side methods. It will
include proper comment about where it is used and how, with description of
current trick

2017-09-13 16:45 GMT+02:00 Marcus Denker :

>
> > On 12 Sep 2017, at 17:33, Guillermo Polito 
> wrote:
> >
> > I don't know... I found the idea of having a Metaclass binding strange...
> >
> > I mean,
> > - metaclasses are not stored in any name dictionary such as Smalltalk
> > - nobody references them directly in source code but by their direct
> classes
> >
> > The metaclass binding is there just for one thing really: methods need
> an association to know their class in case they have to do a super send.
> And transitively this is a compiler problem also. But anybody else accesses
> metaclasses' bindings.
> > ​
> yes, we need it just for the last literal.
>
> We added the “if there is a method, get the binding from there” we adde as
> else
> we would compiler every class side method with a new Association instance,
> which
> wastes lots of space.
>
> Marcus
>

Re: [Pharo-dev] Tricky Metaclass>>binding

[Marcus Denker]

> On 12 Sep 2017, at 17:33, Guillermo Polito  wrote:
> 
> I don't know... I found the idea of having a Metaclass binding strange...
> 
> I mean, 
> - metaclasses are not stored in any name dictionary such as Smalltalk
> - nobody references them directly in source code but by their direct classes
> 
> The metaclass binding is there just for one thing really: methods need an 
> association to know their class in case they have to do a super send. And 
> transitively this is a compiler problem also. But anybody else accesses 
> metaclasses' bindings.
> ​
yes, we need it just for the last literal.

We added the “if there is a method, get the binding from there” we adde as else
we would compiler every class side method with a new Association instance, which
wastes lots of space.

Marcus

Re: [Pharo-dev] Tricky Metaclass>>binding

[Denis Kudriashov]

Yes.
In fact I just want avoid usage of general Association in that places.
So the question do we need two classes for instance and class side
bindings? Or single ClassBinding is enough? In that case class side binding
will have nil as a key (which would be the same for possible
ClassSideBinding)

2017-09-13 9:43 GMT+02:00 Stephane Ducasse :

> At the minimum having classBinding instead of GlobalBinding would be
> already a good step.
> Then since the metaclass and the class are a real couple could we not
> have an object shared by both (but it would cost one indirection).
>
> On Tue, Sep 12, 2017 at 5:33 PM, Guillermo Polito
>  wrote:
> > I don't know... I found the idea of having a Metaclass binding strange...
> >
> > I mean,
> > - metaclasses are not stored in any name dictionary such as Smalltalk
> > - nobody references them directly in source code but by their direct
> classes
> >
> > The metaclass binding is there just for one thing really: methods need an
> > association to know their class in case they have to do a super send. And
> > transitively this is a compiler problem also. But anybody else accesses
> > metaclasses' bindings.
>
>

Re: [Pharo-dev] Tricky Metaclass>>binding

[Stephane Ducasse]

At the minimum having classBinding instead of GlobalBinding would be
already a good step.
Then since the metaclass and the class are a real couple could we not
have an object shared by both (but it would cost one indirection).

On Tue, Sep 12, 2017 at 5:33 PM, Guillermo Polito
 wrote:
> I don't know... I found the idea of having a Metaclass binding strange...
>
> I mean,
> - metaclasses are not stored in any name dictionary such as Smalltalk
> - nobody references them directly in source code but by their direct classes
>
> The metaclass binding is there just for one thing really: methods need an
> association to know their class in case they have to do a super send. And
> transitively this is a compiler problem also. But anybody else accesses
> metaclasses' bindings.

Re: [Pharo-dev] Tricky Metaclass>>binding

[Guillermo Polito]

I don't know... I found the idea of having a Metaclass binding strange...

I mean,
- metaclasses are not stored in any name dictionary such as Smalltalk
- nobody references them directly in source code but by their direct classes

The metaclass binding is there just for one thing really: methods need an
association to know their class in case they have to do a super send. And
transitively this is a compiler problem also. But anybody else accesses
metaclasses' bindings.
​

Re: [Pharo-dev] Tricky Metaclass>>binding

[Marcus Denker]

> On 12 Sep 2017, at 11:32, Denis Kudriashov  wrote:
> 
> I found interesting trick in system: the way how class side perform #binding 
> message:
> 
> Metaclass>>binding
>   "return an association that can be used as the binding
>To share it between methods, reuse an existing one if possible"
>   ^self methodDict 
>   ifEmpty: [nil -> self]
>   ifNotEmpty: [:dict | dict anyOne classBinding]
> 
> It leads to interesting behaviour of class without class side methods:
> 
> NewClass class binding == NewClass class binding "==> false"
> 
> Generally I discovered in the logic which decode class of method in last 
> literal. Interesting that for instance side methods it is always represented 
> by GlobalVariable. And for class side methods it is always general 
> Association.
> 
> Can we make this behaviour more consistent? And will it improve the system? 
> (I thing about possible complications to bootstrap).
> 
> As solution I would introduce new kind of LiteralVariable: ClassBinding with 
> two subclasses InstanceSideBinding and ClassSideBinding. They will take place 
> in last method literal.
> InstanceSideBinding will be used in Smalltalk dictionary for classes instead 
> of GlobalVariable. 
> And it will keep variable with class side binding. So the trick will be not 
> needed anymore. 
> 
> So what do you think?

It would be nice to improve it.. I like the idea of a ClassBinding subclass 
(this way it is distinct from Global Vars, too). The only question of adding 
one ivar to ca. 5000 Objects 
is not too much.. do we get enough out of it for that amount of memory?
Maybe there is some other possibility?

Marcus