On Tue, Aug 5, 2008 at 7:56 PM, Gabriel Dos Reis wrote:
> On Tue, Aug 5, 2008 at 6:47 PM, Bill Page wrote:
>>>
>>> Just eliminating the syntactic transformations in the interpreter
>>> does not solve the problem: you get new failures, and they need to
>>> be resolved. My proposal fort SetAggregate is to replace "<" with
>>> "part?".
>>>
>>
>> Sure, that would solve the immediate problem. If that is all that is
>> of interest then why not just replace those references to '<' with
>> 'subset?' and eliminate the export of '<' from SetAggregate?
>
> The operation subset? does not compute the same thing as "<".
>
Duh... You mean that the documentation in 'SetAggregate'
++ s < t returns true if all elements of set aggregate s are also
++ elements of set aggregate t.
is wrong? I guess that is the case since I see that the definition of
'<' in 'FiniteSetAggregate' is
s < t == #s < #t and s = intersect(s,t)
So you are saying that the intention of SetAggregate is that '<'
denote a "proper" (strict) subset relation.
http://en.wikipedia.org/wiki/Subset
But then '<' is just a (strict) "partial ordering operation" that
obeys a different but related set of axioms. Of course they are
interchangeable because we also have '=' and '~='.
I think this is "harmful" only because of the "misguided syntactic
transformations" that you referred to in the original email. If '<' is
exported by a domain called 'PartiallyOrderedSet', then it's correct
semantics are clear.
Regards,
Bill Page.
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