Assignment 9 for CSCI 431

Running Prolog at UNCA

Some of the problems below can be worked by running the C-Prolog interpreter on Ivy. Here are a few guidelines for using the Prolog interpreter.

• Use the command "cprolog" to invoke the interpreter.
• To exit the interpreter, give the command "halt." (Remember all commands must end with a period.)
• To load the contents of a file into the interpreter (for example, when you have stored your database in a file), give the command "[file_name].", where file_name is the name of the file.
• You can also use the non-hypertext version of the manual for C-Prolog if you prefer that to the one listed on the class page.

Rules Exercises

1. Indicate whether the following are syntactically correct Rules.

   
   a :-  b, c, d:- e f.
   
   happy(X):- a , b.
   
   happy(X):- hasmoney(X) & has_friends(X).
   
   fun(fish):- blue(betty), bike(yamaha).
   

2. Given the database below, indicate whether you think a particular query will succeed or fail.

   
   likes(john,mary).
   likes(john,trains).
   likes(peter,fast_cars).       
   
   likes(Person1,Person2):-
   hobby(Person1,Hobby),      
       hobby(Person2,Hobby).
          
   hobby(john,trainspotting).       
   hobby(tim,sailing). 
   hobby(helen,trainspotting).                       
   hobby(simon,sailing).
   
   ?- likes(john,trains).
   
   ?- likes(helen,john).
   
   ?- likes(tim,helen).
   
   ?- likes(john,helen).
   

Search Exercises

1. Consider the goal ?- fun(What) using the database below.

   
   fun(X) :-              /* fun if .... */                       
           red(X),        /* red */                    
           car(X).            /* and a car */             
   fun(X) :-              /* or its fun if its.... */    
           blue(X),           /* blue */                   
           bike(X).           /* and a bike */       
   
   /* database of red  & blue items */
   red(cricket_ball).        blue(cheese).       
   red(my_hat).              blue(raleigh).        
   red(car_27).              blue(honda).        
                                                  
   /* database of cars  and bikes*/             
   car(peugot).              bike(yamaha).        
   car(rover).               bike(raleigh).     
                             bike(honda).         
   

   Below you will see pairs of goals. These may either be output of a goal e.g. red(my_hat) or calls to another goal e.g. car(my_hat). Indicate which one of the following goal pairs you would expect to see first, for the above query.

   1. fun(X)
      red(X)
   2. blue(cheese)
      red(car_27)
   3. bike(honda)
      bike(yamaha)
   4. blue(cheese)
      bike(raleigh)
   5. bike(X)
      car(X)
   
   
2. Consider the following program.

   
   a(X):-
        b(X), c(X), d(X).
   a(X):-
        c(X), d(X).
   a(X):-
        d(X).
   
   b(1).                             
   b(a).                            
   b(2).
   b(3).
   d(10).
   d(11).
   c(3).
   c(4).
   

   Given the query ?- a(X). Indicate the successive variable bindings that the variable X gets when the above query is run. Separate bindings by a comma (ie. 1,3,5.....)

Lists Exercise

• Here are some problems for which unification sometimes succeeds and sometimes fails. Decide which is the case and, if you think the unification succeeds, write down the substitutions made.
  1. [a,d,z,c] and [H|T]
  2. [apple,pear,grape] and [A,pear|Rest]
  3. [a|Rest] and [a,b,c]
  4. [a,[]] and [A,B|Rest]
  5. [One] and [two|[]]
  6. [one] and [Two]
  7. [a,b,X] and [a,b,c,d]