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Re: >>>BLoCK PROLOG 1st QUERY<<<
Posted:
Feb 9, 2013 1:14 AM
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On Feb 9, 1:18 pm, Graham Cooper <grahamcoop...@gmail.com> wrote:
> QUERY: f [a [b d]] ?
>
>
>
> > TABLE QUERY
> > ref term buds
> > 1 f 0
> > 21 a 0
> > 221 b 0 <-------
> > 222 d 0 <-------
> > 1 * 0
> > 21 * 0
> > 2 * 2
> > 221 * 0
> > 22 * 1 <--------
> > 222 * 0
>
> Simple explanation!
>
> If b and d don't get matched
> you can still match Position 22 to a VAR instead
> and subtract 1 from the expected matched terms!
>
In this example:
f [ a [ b d ]] ? 4 TERM QUERY
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f a D 2 TERM + 1 VAR = 3 MATCHING ROWS
so this SQL clause finds all Predicates with matching terms (all in
the right position)
QUERY.ref=HEADS.ref AND QUERY.term=HEADS.term
GROUP BY HID HAVING COUNT(HID)=$qc-SUM(QB)";
and COUNT(HEAD.ID) = 3
QC = Query Term Count = 4
SUM(BUDS) = 1
So 4-1 = 3 records found!
So it should return this Predicate in the Results.
QUERY: f [a [b d]] 4 - 1 bud
RESULT: f a D 3
EASY!
All that's left is Variable Binding and Tail Recursion..
Herc
--
www.BLoCKPROLOG.com
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