Linas,
On 5/31/19 8:19 AM, Linas Vepstas wrote:
o ExistsLink, ForAllLink,
These are legacy types; they are not used, at all. No one is
implementing the sigma-pi Borel hierarchy in the atomspace. It seemed
like a cool idea a decade ago, and they've mouldered ever since. They
should probably be removed.
Not so fast, these links are used in PLN, well not in any practical
application ATM, but that should change in the future.
PresentLink, AbsentLink---the implementation seems obvious from an
outside perspective/at first glance.
Hah hah. Two weeks ago, I sat down and rolled up my sleeves, and said to
myself: "today is the day I implement AbsentLink as a C++ class". It's
even mentioned in a comment in a recent commit. After laying the
groundwork for this, I realized that it was impossible. Well, maybe not
I thought that AbsentLink implementation was nearly complete, and the
PresentLink implementation possibly already complete but requiring
more testing. I am not correct?
I intend to port all my Atomese code to use PresentLink, can I do so
already? I believe I can but your comment is casting some doubt.
Thanks,
Nil
impossible, but very complicated and confusing, to the point that it
seemed like a recipe for failure and wasted effort. A classical "bad
idea". So I gave up.
Though what could possibly "evaluating a SetLink" mean? ...)
Oh! That's easy! Evaluate all of its members. I am on the verge of
actually implementing that. I haven't, for two reasons:
1) no one is asking for this. There's no obvious need for it.
2) Different external theories might have their own distinct
reason/answer to that question. For example, PLN states that one should
use this-and-such formula to compute the resulting "average" truth
value. But textbook Bayesian probability theory wants to supply you
with a similar, but slightly different answer. And a neural net may
want to provide yet another answer ... this is why Values exist (to
accommodate all these theories), and it is also why "external code does
things with atoms", instead of atoms having methods to do things. The
C++ classes do not have a "Bayesian-probability" method, and a different
"neural-net method", etc. ... on down the line.
3) Turns out SetLinks are evil. Who knew? Took years to figure this out,
and not everyone understands yet. See the wiki page for SetLinks.
-- Linas
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