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[REBOL] Re: Sameness - a pragmatic approach.

From: lmecir:mbox:vol:cz at: 11-Feb-2003 13:51

Hi Gabriele, ----- Original Message ----- From: "Gabriele Santilli" ...
> I don't think the problem is well defined, unless you are able to > identify V amongst any copy of V. > I.e. you would not be able to > solve the problem in this case: > > v: 1 > b: [1] > insert tail b v > So we have two choices: either decide that immutable values that > are equal are to be considered the same value (so that both V and > the two values in the block are the same value), or that immutable > values are never the same (so that we have three different "1"s > above). I am inclined for the latter just because it avoids > another layer of abstraction that is not useful for any other > things except the SAME? function. > > Regards, > Gabriele.
I am not able to identify the position of V uniquely in the case you specified, but my problem is a legal problem even though it may not be uniquely solvable sometimes. The same problem occurs below: v: [1] b: reduce [v] insert/only tail b v and (like you did above), Romano might tell me, that this proves, that indiscernible mutable values are never the same when they are at different positions in a block. Is this reasoning useful for the problem? I doubt it, because my approach gives me the provably optimal solution. Moreover, there is one more trouble with your: "immutable values are never the same" approach. In my article I started by defining the identity and then I was able to define mutations, mutability and immutability. If you start the other way round, then there is a trouble, that you use undefined notions and you have to give the meaning to mutations/mutability first, which may be difficult/ambiguous. (See e.g. the discussion on mutability of dates, etc., where my identity-dependent definition gives different results, than another - yet to be written - definition might yield). Regards -L