[Siop-development] Send by reference or by value?

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

  Question for folks... should the default mode of returning/sending values 
from method calls be by reference or by value for abstract types?  By 
reference would make for better network performance and would be closer to 
the way languages actually function, whereas by value would probably be 
better for compatibility.

  There is also a question of consistency.  Scalar values such as floats, 
integers and booleans always get sent by value by default.  So, if a function 
returns a boolean, SIOP will return to the client a boolean value for that 
platform rather than a reference to a boolean object.  However, as currently 
implemented non-scalar values, like lists and tuples are only returned by 
reference.  You need to make a call to "fetch-value" in order to have the 
server send a copy of those objects back to the client.

  When it comes to parameters, it should be possible to use simple object 
wrappers to indicate to the bridge to send objects by reference or value 
explicitly.  For example:

  remote_object.calculate_some_stuff( by_value( list_of_stuff ) )

  The function above might return another list of values.  Right now, this 
means that the client would receive a proxy that is a referenc to the list on 
the server.  If we changed the policy to be by default by value it a) makes 
the network traffic go up by default and b) makes it more difficult to keep 
the results of an operation on the server.

  Also how would we indicate how to return references by value or by 
reference?

  Maybe we could have by-reference proxies and by-value proxies.

  So, to explicity get the above reference by-value, you could do:

  value_proxy( remote_object ).calculate_some_stuff( list_of_stuff )

  All method calls to the value proxy could call a by value version of 
fetch-attribute and send-message instead of he default.

  Anybody care to venture thoughts?  Does any of this make sense?

  - Rafe