Re: representing 'OR' condition in Prolog.. (removing duplicates efficiently).

[Hector Palacios]

hmmm...

I think thats better:
        leave_granted(Emp) :-
                employee_status(Emp, permanent),!.
        leave_granted(Emp) :-
                performance(Emp, satisfactory).

The cut (!) is a must because you want that
leave_granted return yes only one time.
BTW, it is more efficient that Wolf version.


On Fri, 1 Nov 2002, Robert Wolf wrote:

> Abhinav-Bhardwaj,
> 
> Your program is perfectly correct, this is how you represent "OR" in
> PROLOG.
> To remove duplicates insert negative conditions, something like:
> 
>       leave_granted(Emp) :-
>               employee_status(Emp, permanent),
>               NOT (performance (Emp, satisfactory)).
>       leave_granted(Emp) :-
>               performance(Emp, satisfactory),
>               NOT (employee_status (Emp, permanent)).
> 
> The first condition will "generate" employees, the second will filter
> them out.
> To make your program absolutely "beautifull" insert second clause to
> your report.
> Something like:
>       leave_report :- write ('No (more) answers.').
> This will prevent your report from the "general failure" at the end.

I agree with it.

> 
> Best regards and "happy prologing"...
> 
> Robert P. Wolf
> address@hidden
> 
> 
> -----Original Message-----
> From: Abhinav-Bhardwaj [mailto:address@hidden
> Sent: Thursday, 31 October 2002 5:07 PM
> To: address@hidden
> Subject: representing 'OR' condition in Prolog..
> 
> 
> Hi,
> I want to know something in general about prolog . I want to know that
> how do I represent an 'OR' condition in prolog.
> For eg:- I want to define a leave rule saying that an employee can be
> granted a leave if - employee is a Permanent employee, OR
>           -  employee's performance is satisfactory.
> 
> leave_granted(Emp) :- employee_status(Emp, permanent).
> leave_granted(Emp) :- performance(Emp, satisfactory).
> 
> employee_status( raman, permanent).
> employee_status( abhinav, temporary).
> 
> performance( raman, satisfactory).
> performance( abhinav, satisfactory).
> 
> leave_report :-
>         nl, write('leave may be granted to following employees:-'), nl,
>         leave_granted(Emp),
>         write('-'), write(Emp), nl,
>         fail.
> 
> Here is a sample output:
> =================
> ?- leave_granted(raman).
> 
> yes
> ?- leave_granted(abhinav).
> 
> yes
> ?- leave_report.
> 
> leave may be granted to following employees:-
> -raman
> -raman
> -abhinav
> no
> ==================
> Now my question is:
> 1) Is this a correct way to represent the rule ?
> 2) The 'leave_report' displays the name 'raman' twice , and what I want
> is a list of unique names of employees that can be granted leave.
> 
> thanks and regards,
> Abhinav
> 
> 
> 
> 
> 
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> 
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-- 
++++++++++++++++++++++++++++++++++++++++++++++
Hector L. Palacios V. - Dpto. Computacion y TI
       Grupo de Inteligencia Artificial 
Universidad Simon Bolivar - Caracas, Venezuela

+58-212-9063276(Of)       +58-212-9063243(Fax)
        http://www.ldc.usb.ve/~hlp/
----------------------------------------------
   Ama y haz lo que quieras.    San Agustin.