?-consult soap.

Compiling soap.

Yes.

?-listing.

jealous(A) :-

(loves(A,B) , (loves(C,B) , not (A = C) )).

jealous(A) :-

(married(A,B) , (loves(D,B) , not (A = D) )).

/* as is shown below, ending rule with “not” results only in “yes” or “no” */

loves(phoebe,perry).

loves(jack,phoebe).

loves(lane,phoebe).

loves(jason,eulalie).

married(jason,phoebe).

married(phoebe,jason).

married(perry,stacey).

married(stacey,perry).

married(lane,eulalie).

married(eulalie,lane).

marriage_on_rocks(A,B) :-

(married(A,B) , (loves(A,D) , (not loves(A,B) , (loves(B,_) , (not loves(B,A)

, (nl , (write(' The marriage of ') , (write(A) , (write(' and ') , (write(B) ,

write(' is on the rocks '))))))))))).

marriage_on_rocks(C) :-

(married(C,E) , (loves(C,_) , (loves(E,_) , (not loves(C,E) , (not loves(E,C)

, (write(' The marriage of ') , (write(C) , ' is on the rocks '))))))).

Yes.

?-jealous(Who).

Yes.

?-jealous (jason).

Yes.

?-jealous(phoebe).

No.

?-forget soap.

Yes.

?-consult soap5.

Compiling soap5.

Yes.

?-listing.

jealous(A) :-

(loves(A,B) , (loves(C,B) , (A \= C))). /* red text is changed from not A = C in soap.pro */

jealous(A) :-

(married(A,B) , (loves(D,B) , (A \= D))). /* red text is changed from not A = D in soap.pro */

/* this shows behavioral difference between \= and not */

loves(phoebe,perry).

loves(jack,phoebe).

loves(lane,phoebe).

loves(jason,eulalie).

married(jason,phoebe).

married(phoebe,jason).

married(perry,stacey).

married(stacey,perry).

married(lane,eulalie).

married(eulalie,lane).

marriage_on_rocks(A,B) :-

(married(A,B) , (loves(A,D) , (not loves(A,B) , (loves(B,_) , (not loves(B,A)

, (nl , (write(' The marriage of ') , (write(A) , (write(' and ') , (write(B) ,

write(' is on the rocks '))))))))))).

marriage_on_rocks(C) :-

(married(C,E) , (loves(C,_) , (loves(E,_) , (not loves(C,E) , (not loves(E,C)

, (write(' The marriage of ') , (write(C) , write(' is on the rocks ')))))))).

Yes.

?-jealous(Who).

Who = jack

More? (Y/N):y

Who = lane

More? (Y/N):y

Who = jason

More? (Y/N):y

Who = jason

More? (Y/N):y

Who = stacey

More? (Y/N):y

Who = lane

More? (Y/N):y

No.

?-forget soap5.

Yes.

?-consult soap2.

Compiling soap2.

Yes.

?-listing.

jealous(A) :-

(loves(A,B) , (loves(C,B) , (not (A = C) , (nl , (write(A) , write(' is jealous first ')))))).

jealous(A) :-

(married(A,B) , (loves(D,B) , (not (A = D) , (nl , (write(A) , write(' is jealous ')))))).

/* red text added to soap.pro to force output other than “yes” or “no”.*/

/* alternative to using \= to get output other than “yes” or “no”. */

loves(phoebe,perry).

loves(jack,phoebe).

loves(lane,phoebe).

loves(jason,eulalie).

married(jason,phoebe).

married(phoebe,jason).

married(perry,stacey).

married(stacey,perry).

married(lane,eulalie).

married(eulalie,lane).

marriage_on_rocks(A,B) :-

(married(A,B) , (loves(A,D) , (not loves(A,B) , (loves(B,_) , (not loves(B,A)

, (nl , (write(' The marriage of ') , (write(A) , (write(' and ') , (write(B) ,

write(' is on the rocks '))))))))))).

marriage_on_rocks(C) :-

(married(C,E) , (loves(C,_) , (loves(E,_) , (not loves(C,E) , (not loves(E,C)

, (write(' The marriage of ') , (write(C) , write(' is on the rocks ')))))))).

Yes

?-jealous(Who).

jack' is jealous first '

Who = jack

More? (Y/N):y

lane' is jealous first '

Who = lane

More? (Y/N):y

jason' is jealous '

Who = jason

More? (Y/N):y

jason' is jealous '

Who = jason

More? (Y/N):y

stacey' is jealous '

Who = stacey

More? (Y/N):y

lane' is jealous '

Who = lane

More? (Y/N):y

No.

forget soap2.

?-consult soap4.

Compiling soap4.

Yes.

?-listing.

jealous(A) :-

(loves(A,B) , (loves(C,B) , ((A \= C) , (nl , (write(A) , write(' is jealous first ')))))).

jealous(A) :-

(married(A,B) , (loves(D,B) , ((A \= D) , (nl , (write(A) , write(' is jealous second ')))))).

/* green text added to soap2.pro to distinguish which results come from which jealous */

loves(phoebe,perry).

loves(jack,phoebe).

loves(lane,phoebe).

loves(jason,eulalie).

married(jason,phoebe).

married(phoebe,jason).

married(perry,stacey).

married(stacey,perry).

married(lane,eulalie).

married(eulalie,lane).

marriage_on_rocks(A,B) :-

(married(A,B) , (loves(A,D) , (not loves(A,B) , (loves(B,_) , (not loves(B,A)

, (nl , (write(' The marriage of ') , (write(A) , (write(' and ') , (write(B) ,

write(' is on the rocks '))))))))))).

marriage_on_rocks(C) :-

(married(C,E) , (loves(C,_) , (loves(E,_) , (not loves(C,E) , (not loves(E,C)

, (write(' The marriage of ') , (write(C) , write(' is on the rocks ')))))))).

Yes.

?-jealous(Who).

jack' is jealous first '

Who = jack

More? (Y/N):y

lane' is jealous first '

Who = lane

More? (Y/N):y

jason' is jealous second '

Who = jason

More? (Y/N):y

jason' is jealous second '

Who = jason

More? (Y/N):y

stacey' is jealous second '

Who = stacey

More? (Y/N):y

lane' is jealous second '

Who = lane

More? (Y/N):y

No.

?-forget soap4.

Yes.

?-consult soap3.

Compiling soap3.

Yes.

?-listing.

jealous(A) :-

(loves(A,B) , (loves(C,B) , (not (A = C) , (nl , (write(A) , write(' is jealous

first ')))))).

jealous(A) :-

(married(A,B) , (loves(D,B) , (nl , (write(A) , write(' is jealous second '))))).

/* removed not A= D from soap2.pro to see whether it was needed */

/* it wasn’t in THIS database but might be necessary in another context */

loves(phoebe,perry).

loves(jack,phoebe).

loves(lane,phoebe).

loves(jason,eulalie).

married(jason,phoebe).

married(phoebe,jason).

married(perry,stacey).

married(stacey,perry).

married(lane,eulalie).

married(eulalie,lane).

marriage_on_rocks(A,B) :-

(married(A,B) , (loves(A,D) , (not loves(A,B) , (loves(B,_) , (not loves(B,A)

, (nl , (write(' The marriage of ') , (write(A) , (write(' and ') , (write(B) ,

write(' is on the rocks '))))))))))).

marriage_on_rocks(C) :-

(married(C,E) , (loves(C,_) , (loves(E,_) , (not loves(C,E) , (not loves(E,C)

, (write(' The marriage of ') , (write(C) , write(' is on the rocks ')))))))).

Yes.

?-jealous(Who).

jack' is jealous first '

Who = jack

More? (Y/N):y

lane' is jealous first '

Who = lane

More? (Y/N):y

jason' is jealous second '

Who = jason

More? (Y/N):y

jason' is jealous second '

Who = jason

More? (Y/N):y

stacey' is jealous second '

Who = stacey

More? (Y/N):y

lane' is jealous second '

Who = lane

More? (Y/N):y

No.