47 unit tests fail ... I'm not sure if they all fail for the same reason,
though.
For example PutLink
(PutLink
(LambdaLink
(VariableList
(TypedVariableLink
(VariableNode "$X")
(TypeNode "PredicateNode")
)
(TypedVariableLink
(VariableNode "$Y")
(TypeNode "PredicateNode")
)
)
(AndLink
(EvaluationLink
(PredicateNode "acquainted")
(ListLink
(VariableNode "$X")
(VariableNode "$Y")
)
)
(ImplicationLink
(VariableNode "$X") ; this is alpha-converted to $foo1233
(PredicateNode "is-human")
)
(ImplicationLink
(VariableNode "$X") ; this is alpha-converted to $bar456
(PredicateNode "is-human")
)
)
)
(ListLink
(PredicateNode "is-Self")
(PredicateNode "is-Bob")
)
)
So, because the implication link is scoped, the result of the variable
substitution is
(AndLink
(ImplicationLink
(VariableNode "$foo123")
(PredicateNode "is-human")
)
(ImplicationLink
(VariableNode "$bar456")
(PredicateNode "is-human")
)
(EvaluationLink
(PredicateNode "acquainted")
(ListLink
(PredicateNode "is-Self")
(PredicateNode "is-Bob")
)
)
)
which is not what the unit test expects. The problem with using either
ScopeLink or LambdaLink is that it becomes impossible to have a stable
variable name -- it can be alpha-converted to anything, so any algo that
depends on having a fixed, well-known variable name will fail.
In this case -- I am not sure -- if you want ImplicationLink to be scoped,
then the unit test is wrong. But is the unit test is right, then
implication link must not be scoped. I cannot tell which one is wanted.
--linas
On Tue, Oct 11, 2016 at 12:12 PM, Nil Geisweiller <ngeis...@googlemail.com>
wrote:
> Linas,
>
> I don't have time to get into that right now. If you can point to where
> exactly it breaks (like a unit test on your branch) it would help. In any
> case I look carefully into that and reply tomorrow.
>
> Nil
>
>
> On 10/11/2016 06:55 PM, Linas Vepstas wrote:
>
>> You made it inherit from ScopeLink, thus making the variables in it
>> implicitly scoped. Then you added the file ImplicationLink.cc, and have
>> notes in there, complaining about how variables are implcitly scoped.
>> The wiki page for it, http://wiki.opencog.org/w/ImplicationLink still
>> says things that are wrong (re alpha conversion -- each lambda gets
>> alpha converted, so the "sugar syntax" section cannot possibly be right).
>>
>> I'm asking, because I'm trying to fix #910 by doing the alpha conversion
>> correctly, and the result of the fix is that unit tests with implication
>> links in them now fail. The whole thing smells bad.
>>
>> Either ImplicationLinks do inherit from ScopeLink, in which case, there
>> should be no complaints about how the ScopeLink works: it does the right
>> thing. If you don't like what the scopeLink does, then ImplicationLinks
>> should NOT inherit from it ...
>>
>> In either case, the wiki page needs fixing, because the alpha conversion
>> conversation we had recently renders that page incoherent.
>>
>> I don't really care, one way or the other, but I do need to understand
>> the intended design well enough to be able to fix bugs, and right now, I
>> don't understand what ImplicationLink is, or how its supposed to work.
>>
>> --linas
>>
>>
>>
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