1. How To Think Like a Prolog ?
Done by :
Asma Almane , Banan Alhadlaq

2. Example 1: Consider the following Prolog program:
Q: As a compiler , find the possible answers of X in the following query : ? – predecessor ( X , jim ) .
parent(pam,bob).
parent(tom,bob).
parent(tom,liz).
parent(bob,ann).
parent(bob,pat).
parent(pat,jim).
predecessor(X,Z):-
parent(X,Z).
parent(X,Y),
predecessor(Y,Z).

3. Example 1: Consider the following Prolog program:
? – predecessor ( X , jim ) .
Example 1: Consider the following Prolog program:
predecessor(X,jim)
By using rule pr1
From the fact parent (pat,jim)
X = pat , Z = jim
parent(pam,bob).
parent(tom,bob).
parent(tom,liz).
parent(bob,ann).
parent(bob,pat).
parent(pat,jim).
predecessor(X,Z):-
parent(X,Z).
parent(X,Y),
predecessor(Y,Z).
parent(pat,jim)
TRUE
X= pat ;

4. Example 1: Consider the following Prolog program:
? – predecessor ( X , jim ) .
Example 1: Consider the following Prolog program:
predecessor(X,jim)
By using rule pr 2
From the fact Parent(pam,bob).
X=pam , Y=bob
parent( pam , bob ) ,
predecessor(bob , jim).
parent(pam,bob).
parent(tom,bob).
parent(tom,liz).
parent(bob,ann).
parent(bob,pat).
parent(pat,jim).
predecessor(X,Z):-
parent(X,Z).
parent(X,Y),
predecessor(Y,Z).
predecessor(bob , jim).
By using rule pr 2
By using rule pr 1
From the fact Parent(bob,ann).
X=bob , Y=ann
parent( bob , jim ).
parent( bob , ann ),
predecessor( ann , jim).
FALSE
predecessor( ann , jim).
By using rule pr 1
By using rule pr 2
parent( ann , jim).
parent( ann , Y ),
predecessor( Y , jim).
FALSE
FALSE

5. Example 1: Consider the following Prolog program:
? – predecessor ( X , jim ) .
Example 1: Consider the following Prolog program:
predecessor(X,jim)
By using rule pr 2
From the fact Parent(pam,bob).
X=pam , Y=bob
parent( pam , bob ) ,
predecessor(bob , jim).
parent(pam,bob).
parent(tom,bob).
parent(tom,liz).
parent(bob,ann).
parent(bob,pat).
parent(pat,jim).
predecessor(X,Z):-
parent(X,Z).
parent(X,Y),
predecessor(Y,Z).
predecessor(bob , jim).
By using rule pr 2
By using rule pr 1
From te fact Parent(bob,pat).
X=bob , Y=ann
parent( bob , jim ).
parent( bob , pat ),
predecessor( pat , jim).
FALSE
predecessor( pat , jim).
By using rule pr 1
parent( pat , jim).
X=pam ;
TRUE

6. Example 1: Consider the following Prolog program:
? – predecessor ( X , jim ) .
Example 1: Consider the following Prolog program:
predecessor(X,jim)
By using rule pr 2
From the fact Parent(pam,bob).
X=tom , Y=bob
parent( tom , bob ) ,
predecessor(bob , jim).
parent(pam,bob).
parent(tom,bob).
parent(tom,liz).
parent(bob,ann).
parent(bob,pat).
parent(pat,jim).
predecessor(X,Z):-
parent(X,Z).
parent(X,Y),
predecessor(Y,Z).
predecessor(bob , jim).
By using rule pr 2
By using rule pr 1
From the fact Parent(bob,ann).
X=bob , Y=ann
parent( bob , jim ).
parent( bob , ann ),
predecessor( ann , jim).
FALSE
predecessor( ann , jim).
By using rule pr 1
By using rule pr 2
parent( ann , jim).
parent( ann , Y ),
predecessor( Y , jim).
FALSE
FALSE

7. Example 1: Consider the following Prolog program:
? – predecessor ( X , jim ) .
Example 1: Consider the following Prolog program:
predecessor(X,jim)
By using rule pr 2
From the fact Parent(pam,bob).
X=tom , Y=bob
parent( tom , bob ) ,
predecessor(bob , jim).
parent(pam,bob).
parent(tom,bob).
parent(tom,liz).
parent(bob,ann).
parent(bob,pat).
parent(pat,jim).
predecessor(X,Z):-
parent(X,Z).
parent(X,Y),
predecessor(Y,Z).
predecessor(bob , jim).
By using rule pr 2
By using rule pr 1
From the fact Parent(bob,pat).
X=bob , Y=ann
parent( bob , jim ).
parent( bob , pat ),
predecessor( pat , jim).
FALSE
predecessor( pat , jim).
By using rule pr 1
parent( pat , jim).
X=tom ;
TRUE

8. Example 1: Consider the following Prolog program:
? – predecessor ( X , jim ) .
Example 1: Consider the following Prolog program:
predecessor(X,jim)
By using rule pr 2
From the fact Parent(pam,bob).
X=tom , Y=liz
parent( tom , liz ) ,
predecessor(liz , jim).
parent(pam,bob).
parent(tom,bob).
parent(tom,liz).
parent(bob,ann).
parent(bob,pat).
parent(pat,jim).
predecessor(X,Z):-
parent(X,Z).
parent(X,Y),
predecessor(Y,Z).
predecessor(liz , jim).
By using rule pr 1
By using rule pr 2
parent( liz , jim ).
parent( liz , Y ),
predecessor( Y , jim).
FALSE
There is NO Y
FALSE

9. Example 1: Consider the following Prolog program:
? – predecessor ( X , jim ) .
Example 1: Consider the following Prolog program:
predecessor(X , jim).
By using rule pr 2
From the fact Parent(bob,ann).
X=bob , Y=ann
parent(pam,bob).
parent(tom,bob).
parent(tom,liz).
parent(bob,ann).
parent(bob,pat).
parent(pat,jim).
predecessor(X,Z):-
parent(X,Z).
parent(X,Y),
predecessor(Y,Z).
parent( bob , ann ),
predecessor( ann , jim).
predecessor( ann , jim).
By using rule pr 1
By using rule pr 2
parent( ann , jim).
parent( ann , Y ),
predecessor( Y , jim).
FALSE
There is NO Y
FALSE

10. Example 1: Consider the following Prolog program:
? – predecessor ( X , jim ) .
Example 1: Consider the following Prolog program:
predecessor(X,jim)
By using rule pr 2
From the fact Parent(bob,pat).
X=bob , Y=pat
parent( bob , pat ),
predecessor( pat , jim).
parent(pam,bob).
parent(tom,bob).
parent(tom,liz).
parent(bob,ann).
parent(bob,pat).
parent(pat,jim).
predecessor(X,Z):-
parent(X,Z).
parent(X,Y),
predecessor(Y,Z).
predecessor( pat , jim).
By using rule pr 1
parent( pat , jim).
TRUE
X=bob ;

11. Example 1: Consider the following Prolog program:
? – predecessor ( X , jim ) .
Example 1: Consider the following Prolog program:
predecessor(X,jim)
By using rule pr 2
parent( pat , jim ),
predecessor( jim , jim).
parent(pam,bob).
parent(tom,bob).
parent(tom,liz).
parent(bob,ann).
parent(bob,pat).
parent(pat,jim).
predecessor(X,Z):-
parent(X,Z).
parent(X,Y),
predecessor(Y,Z).
predecessor( jim , jim).
By using rule pr 1
By using rule pr 2
parent( jim , jim).
parent( jim , Y ),
predecessor( Y , jim).
FALSE
There is NO Y
FALSE

12. Example 2: Consider the following Prolog program:
Q: As a compiler , find the possible answers of X and Y in the following query : ? – brother ( X , Y ) .
father(ahmad,sami).
father(ahmad,khalid).
father(sami,fahad).
father(sami,mohammed).
father(khalid,naseer).
brother(X,Y):-
father(Z,X) ,
father(Z,Y),
not(X=Y).

13. Example 2: Consider the following Prolog program:
? – brother ( X , Y ) .
Example 2: Consider the following Prolog program:
brother ( X , Y )
father(ahmad,sami).
father(ahmad,khalid).
father(sami,fahad).
father(sami,mohammed).
father(khalid,naseer).
brother(X,Y):-
father(Z,X) ,
father(Z,Y),
not(X=Y).
By using the facts
father (ahmad , sami) ,
father (ahmed,Y) ,
not(sami=Y).
TRUE ;
X= sami , Y=khalid

14. Example 2: Consider the following Prolog program:
? – brother ( X , Y ) .
Example 2: Consider the following Prolog program:
brother ( X , Y )
father(ahmad,sami).
father(ahmad,khalid).
father(sami,fahad).
father(sami,mohammed).
father(khalid,naseer).
brother(X,Y):-
father(Z,X) ,
father(Z,Y),
not(X=Y).
By using the facts
father (ahmad , khalid) ,
father (ahmed,Y) ,
not(khalid=Y).
TRUE ;
X= khalid , Y=sami

15. Example 2: Consider the following Prolog program:
? – brother ( X , Y ) .
Example 2: Consider the following Prolog program:
brother ( X , Y )
father(ahmad,sami).
father(ahmad,khalid).
father(sami,fahad).
father(sami,mohammed).
father(khalid,naseer).
brother(X,Y):-
father(Z,X) ,
father(Z,Y),
not(X=Y).
By using the facts
father (sami , fahad) ,
father (sami,Y),
Not(fahad=Y).
TRUE
X= fahad , Y=mohammed ;

16. Example 2: Consider the following Prolog program:
? – brother ( X , Y ) .
Example 2: Consider the following Prolog program:
brother ( X , Y )
father(ahmad,sami).
father(ahmad,khalid).
father(sami,fahad).
father(sami,mohammed).
father(khalid,naseer).
brother(X,Y):-
father(Z,X) ,
father(Z,Y),
not(X=Y).
By using the facts
father (sami,mohammed),
father(sami,Y),
not(mohammed=Y).
TRUE
X=mohammed , Y= fahad ;

17. Example 2: Consider the following Prolog program:
? – brother ( X , Y ) .
Example 2: Consider the following Prolog program:
brother ( X , Y )
father(ahmad,sami).
father(ahmad,khalid).
father(sami,fahad).
father(sami,mohammed).
father(khalid,naseer).
brother(X,Y):-
father(Z,X) ,
father(Z,Y),
not(X=Y).
By using the facts
father (khalid,naseer),
father(khalid,Y),
not(naseer=Y).
FALSE
false.