Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uunet!munnari.oz.au!bruce!jono
From: jono@bruce.OZ (Jonathan Oliver)
Newsgroups: comp.lang.prolog
Subject: The jobs puzzle revisted
Message-ID: <1683@bruce.OZ>
Date: 10 Nov 89 05:57:43 GMT
Organization: Monash Uni. Computer Science, Australia
Lines: 132

In reply to the following article we present a solution closer
to the problem statement:

> From LAZBM%CUNYVM.CUNY.EDU@munnari Mon Oct  2 23:51:15 1989
> Path: bruce!munnari.oz.au!murtoa.cs.mu.oz.au!uunet!ginosko!gem.mps.ohio-state.edu!wuarchive!psuvax1!psuvm!cunyvm.bitnet!lazbm
> From: LAZBM@CUNYVM.CUNY.EDU
> Newsgroups: comp.lang.prolog
> Subject: The jobs puzzle
> Message-ID: <2572LAZBM@CUNYVM>
> Date: 2 Oct 89 13:51:15 GMT
> Organization: The City University of New York - New York, NY
> Lines: 54
> DISCLAIMER: Author bears full responsibility for contents of this article
> 
>  This is my solution to the jobs puzzle.
>  It works, but it would be nice to write down the problem and that would
>  be the solution.
>  Anybody has a better solution?
> 
> /* The jobs puzzle
>  * 1  There are four people roberta thelma steve and pete
>  * 2  Among them,they hold eight different jobs
>  * 3  Each holds exactly 2 jobs
>  * 4  The jobs are:chef,guard,nurse,telephone operator,
>  *        police officer(gender not implied) teacher actor boxer
>  * 5  The job of nurse is held by a male
>  * 6  The husband of the chef is the telephone operator
>  * 7  Roberta is not the boxer
>  * 8  Pete has no education past ninth grade
>  * 9  Roberta, the chef and the police officer went golfing together
>  */
> solve:-joblist(Jlist),
>        del(J1,Jlist,Jl1),del(J2,Jl1,Jl2),J1 < J2 ,hasjobs(roberta,J1,J2),
>        del(J3,Jl2,  Jl3),del(J4,Jl3,Jl4),J3 < J4 ,hasjobs(thelma ,J3,J4),
>        del(J5,Jl4  ,Jl5),del(J6,Jl5,Jl6),J5 < J6 ,hasjobs(steve  ,J5,J6),
>        del(J7,Jl6  ,Jl7),del(J8,Jl7,Jl8),J7 < J8 ,hasjobs(pete   ,J7,J8),
>        write('roberta '),write(J1),write(' '),write(J2),nl,
>        write('thelma  '),write(J3),write(' '),write(J4),nl,
>        write('steve   '),write(J5),write(' '),write(J6),nl,
>        write('pete    '),write(J7),write(' '),write(J8),nl.
> 
> hasjobs(X,chef,police):-!,fail.      /*9 */
> hasjobs(X,police,chef):-!,fail.      /*9 */
> hasjobs(X,telop,chef):-!,fail.       /*6 */
> hasjobs(X,chef,telop):-!,fail.       /*6 */
> hasjobs(X,J1,J2):- hasjob(X,J1),
>                    hasjob(X,J2).
> 
> hasjob(roberta,chef):-!,fail.       /*9 */
> hasjob(roberta,police):-!,fail.     /*9 */
> hasjob(pete,police):-!,fail.        /*8*/
> hasjob(pete,nurse ):-!,fail.        /*8*/
> hasjob(pete,teacher):-!,fail.       /*8*/
> hasjob(roberta,boxer):- !,fail.     /*7*/
> hasjob(X,nurse):- !,male(X).        /*5*/
> hasjob(X,actor):- !,male(X).                 /* meaning of actor*/
> hasjob(X,telop):-!,male(X).         /*6 */
> hasjob(X,chef ):-!,not male(X).     /*6 */
> hasjob(X,Y).
> 
> male(steve).
> male(pete ).
> 
> /* list symbol is { } in this prolog */
> joblist({chef,guard,nurse,telop,police,teacher,actor,boxer}).
> del(X,{X|T},T).
> del(X,{Y|T},{Y|T1}) :- del(X,T,T1).
> 

Our Solution

-------------------------------------------------------------------------

/* The problem is set out in a similar way to the Zebra Problem */
/* tested on mu_prolog version 3.1 */
/* person(name, jobs, gender) */

not_job(L, P, Job) :-
	member(person(P, J, _), L),
	member(Job, J), !, fail.
not_job(L, _, _).

s(L):-
	L = [	person(_, [_,_], _), person(_, [_,_], _),
		person(_, [_,_], _), person(_, [_,_], _) ],
/* Sex */
	member(person(thelma, _, female), L),
	member(person(roberta, _, female), L),
	member(person(steve, _, male), L),
	member(person(pete, _, male), L),
/* 5. nurse is a male */
	member(person(_, J1, male), L),
	member(nurse, J1),
/* 6. husband of chef is telephone */
	member(person(_, J2, female), L),
	member(chef, J2),
	member(person(_, J3, male), L),
	member(teleop, J3),
/* define police, boxer, teacher, guard and actor as jobs */
	member(person(_, J4, _), L), member(police, J4),
	member(person(_, J5, _), L), member(boxer, J5),
	member(person(_, J6, _), L), member(teacher, J6),
	member(person(_, J7, _), L), member(guard, J7),
	member(person(_, J8, _), L), member(actor, J8),
/* 7. roberta is not the boxer */
	not_job(L, roberta, boxer),
/* 8. pete has no education beyond 9th grade */
	/* The problem doesn't state explicitly which jobs are excluded
	so we assume that the following jobs are excluded:
		nurse, police and teacher */
	not_job(L, pete, nurse),
	not_job(L, pete, police),
	not_job(L, pete, teacher),
/* 9. roberta the chef the police went golfing together */
	not_job(L, roberta, police),
	not_job(L, roberta, chef),
	not_both(L).

member(X,[X|_]).
member(X,[_|Y]) :- member(X,Y).

/* not_both is derived from statement 9 */
not_both(L) :-
	member(person(_, [police, chef], _) , L), !, fail.
not_both(L) :-
	member(person(_, [chef, police], _) , L), !, fail.
not_both(L).



-------------------------------------------------------------------------
	Jon Oliver and Pierre Lim.