Re: Ocaml binding innards (was Re: [gdome]user_data and language bindings)

[Claudio Sacerdoti Coen <sacerdot CS UniBO IT>]

> "newChild" are the very same object inside Ocaml for this particular
> method (insertBefore), and not two different Ocaml objects that happen to
> represent the same Gdome node?
> ...
> n1 = someNode.firstChild
> n2 = someNode.firstChild
> (in whatever Syntax is appropriate for Ocaml),
> n1 and n2 are different Ocaml objects that happen to wrap the same gdome
> node. With different I mean, they would fail at least some of Ocaml's
> equality/identity tests.

 Yeah, you got it right!

 Let's say something on equality in Ocaml. In Ocaml we are used to two
 kinds of equality: structural equality and phisical equality. Physical
 equality means that the two objects are the same, i.e. they have the
 same address in memory. The other equality means that all of their fields
 are equal. The equality for binded objects is physical equality.

 So you are right: physical equality is broken (while structural equality
 is retained, but also a bit less efficient). By the way:

  1) Structural equality seems to be the preferred/standard equality for Ocaml.
     (For some reasons I don't want to explain here.)
  2) If you really need physical equality, than it is usually up to you to
     grant in your code that it is preserved. In this case I could either
     use the user_data field as you did, or use the global (per-document)
     hash-table technique. The fact that physical equality is less used
     suggests me that the hash-table technique is probably better.


 By the way, thank you for helping me focusing on this point. I should
 probably add it to the documentation of the binding in the next
 release.

 					Regards,
					C.S.C.

-- 
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Real name: Claudio Sacerdoti Coen
PhD Student in Computer Science at University of Bologna
E-mail: sacerdot cs unibo it
http://caristudenti.cs.unibo.it/~sacerdot
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