Re: Simple Question

Brent Fulgham <[email protected]> writes:

> How do I "query" my assertions, as I might with a standard Prolog-
> style database.
[...]
> Welcome to OpenMCL Version 1.0 (DarwinPPC32)!
[...]
> ? (facts)
> #<FACT F-0, HOBBIT, CF is 0.000 ; ((AGE 100) (NAME FRODO))>
> #<FACT F-1, HOBBIT, CF is 0.000 ; ((AGE 200) (NAME BILBO))>
[...]
> ? (retrieve (?x)
> (?x (hobbit (name ?name))))
> ;Compiler warnings :
> ;   Unused lexical variable #:G30, in an anonymous lambda form.
> (((?X . #<HOBBIT #x844F246>)) ((?X . #<HOBBIT #x84397BE>)))

The query works for me with CMUCL under Linux.  It returns:

  (((?X . #<HOBBIT {594097F5}>)) ((?X . #<HOBBIT {593FA3B5}>)))

This may be an OpenMCL issue.


> Fine -- but how can I display this data?  For example, how can I
> construct a rule that lists all hobbits who are over 100?  Or even

You may try something like this:

  (defrule old-hobbit ()
    (?h (hobbit (age ?age (> ?age 100))))
     =>
    (format t "~&Found: ~A~%" ?h))

which returns:

  Found: #<FACT F-2, HOBBIT, CF is 0.000 ; ((AGE 200) (NAME BILBO))>


> iterate over the values to display them?
>
> I think I can do so using "with-simple-query", but a few examples
> might help.

WITH-SIMPLE-QUERY is probably the right way, but I also don't know how
it works and would appreciate an example as well.


Paolo
-- 
Lisp Propulsion Laboratory log - http://www.paoloamoroso.it/log


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