siop-development

[Siop-development] Passing by value and by reference

[Rapheal K. <ra...@ma...>]

  I've added a "ref" and "val"... err... modifier?  Not sure what to call 
them.  They are intended to be simple markers that a host language can use as 
a hint to the bridge so that the bridge knows to over-ride the default 
parameter behavior for an object being passed to a peer either via parameters 
or return value.

  Remember, scalar values are passed by value by default while collections are 
passed by reference by default.  These little keyword thingies can over-ride 
this default behavior.  So, let's say you were calling a method that uses a 
list.  It might be the case that the programmer can figure out that it would 
be an optimization to send the list to the other side, especially if the code 
over there does a lot of random access:

  remote_object.helpful_method( val( [ "a", "b", "c", "d" ] ) )

  The example above would send a reference to the list if it were not for the 
modifier wrapper object.

  This is very useful in the example wxWidgets code where we needed to 
construct native Python tuples and dictionaries in order to be able to create 
new classes:

    # Helper method to define Python types
    # Class creation requires actual Python tuples, not pretenders
    # TODO: This can be disposed of when it is possible to pass
    # tuples by-value
    def tuple( *stuff  )
        list = $types.ListType.call
        for thing in stuff
            list.append( thing )
        end
        $types.TupleType( list )
    end

    # Helper method to define Python class
    # In the future, may provide helper library to do this
    def pyclass( name, *parents, &definition )
        klass = $types.ClassType(   name.to_s,
                                tuple( *parents ),
                                $types.DictType.call
                                )
        klass.instance_eval &definition unless definition.nil?
        klass
    end


  Now it's a little easier:


    # Helper method to define Python class
    # In the future, may provide helper library to do this
    def pyclass( name, *parents, &definition )
        klass = $types.ClassType(   name.to_s,
                                Siop::val( Siop::Tuple( *parents ) ),
                                Siop::val( {} )
                                )
        klass.instance_eval &definition unless definition.nil?
        klass
    end

  Anyone who thinks they follow this and cares to voice their opinion as to 
wether this seems ok or is cumbersome, or thinks there might be a more 
preferable way, please tell me.

  - Rafe

Re: [Siop-development] Passing by value and by reference

[Kevin S. <wx...@qu...>]

On Thu, 2006-06-29 at 00:43 -0700, Rapheal Kaplan wrote:
>   I've added a "ref" and "val"... err... modifier?  Not sure what to call 
> them.  

Seems ok.

>   Remember, scalar values are passed by value by default while collections are 
> passed by reference by default.  

Still sounds irritating to me, as one who is constantly fuming about the
scalar/object distinction in Java. Maybe this wouldn't be so bad, since
as I mentioned Ruby passes ints by reference but they appear to be
passed by value since they are immutable.

>   Now it's a little easier:
> 
> 
>     # Helper method to define Python class
>     # In the future, may provide helper library to do this
>     def pyclass( name, *parents, &definition )
>         klass = $types.ClassType(   name.to_s,
>                                 Siop::val( Siop::Tuple( *parents ) ),
>                                 Siop::val( {} )
>                                 )
>         klass.instance_eval &definition unless definition.nil?
>         klass
>     end

I would hope that code like this would be part of the siop framework, at
least at some point. You're not going to expect a siop user like me to
write or maintain code like that, are you? 

I had a similar reaction to the wxRython snippets...they seemed to be a
mix of generic and specific code. I don't want to see the sausage-making
generic code. It's all about encapsulating the icky parts into the
framework so clients like us can just use remote classes and objects as
if they were local.

Something like this would be cool:

  class MyApp < siop.remote_class(:wx, :App)
    def on_init
      # blah blah blah
    end
  end

Kevin

Re: [Siop-development] Passing by value and by reference

[Rapheal K. <ra...@ma...>]

>>   Now it's a little easier:
>>
>>
>>     # Helper method to define Python class
>>     # In the future, may provide helper library to do this
>>     def pyclass( name, *parents, &definition )
>>         klass = $types.ClassType(   name.to_s,
>>                                 Siop::val( Siop::Tuple( *parents ) ),
>>                                 Siop::val( {} )
>>                                 )
>>         klass.instance_eval &definition unless definition.nil?
>>         klass
>>     end
>>     
>
> I would hope that code like this would be part of the siop framework, at
> least at some point. You're not going to expect a siop user like me to
> write or maintain code like that, are you? 
>
>   
  Meaning, siop will include code for creating classes?  I think that 
class creation should be one of the levels.  Then it would be a lot 
simpler to code the above thingy.  There would, for one, be no need to 
do the val thing nor the tuple thing, because the bridge on the 
receiving side could take care of all of that for you.



> I had a similar reaction to the wxRython snippets...they seemed to be a
> mix of generic and specific code. I don't want to see the sausage-making
> generic code. It's all about encapsulating the icky parts into the
> framework so clients like us can just use remote classes and objects as
> if they were local.
>
> Something like this would be cool:
>
>   class MyApp < siop.remote_class(:wx, :App)
>     def on_init
>       # blah blah blah
>     end
>   end
>   

  Right, that's what I am thinking.