CSE505 – Assignment 3 – Problem 2 Solved

CSE505 – Assignment 3 – Problem 2 

You may work in the same team as for A3 Problem 1 

Unzip the directory A3_Problem2.zip and refer to the Tiny OOPL program given in tinyoopl.txt – a portion of this file is shown on the next page.   It gives the outline of an object-oriented program consisting of classes, fields, and methods, but without the bodies of methods.  The constructs of a TINY OOPL program can be encoded in three relations:

 

db_class(C1, C2) –  meaning, class C1 extends class C2 

db_field(C, F:T) –  meaning, class C declares field F with type T           

                           (where : is an infix binary constructor) 

db_method(C, M:T1-T2) –  class C declares method M with type T1-T2, where T2 is void                                                     when M is a void method  (and - is an infix binary constructor)

The file database.pl shows instances of these relations for the program in tinyoopl.txt, and a sample from this file reproduced on the next page. Using these relations, define the following Prolog predicates:

 

a.     subclass(C1,C2):  Given C2 as input, return in C1 every subclass of C2, one-by-one upon backtracking.  And, given C1 as input, return in C2 every superclass of C1, one-byone upon backtracking.   Note: the terms superclass and subclass refer not only to the immediate super/subclass, but also the super/subclasses that are obtained transitively.

 

b.     recursive(C):  Given a class C as input, return true/false indicating whether C is recursive, i.e., whether C or one of its subclasses declares a field of type C.  

 

c.     over_ridden(B,C,M,T):  A method M of type T in class C is said to be over-ridden relative a class B if either B or some superclass B2 of B (where B2 is a subclass of C) also defines method M of type T.

 

d.     inherits(C,L):  Given a class C as input, return in L the list of all C2:M:T where M:T is a declared (but not an over-ridden) method of some superclass class C2 of C, and T is M’s declared type.  The predicate should fail if C has no such methods.

 

e.     cycle(C): Return true/false indicating whether there is a cycle through some method of class C.  We say there is a cycle through a method of class C if the method has a parameter with type (class) C or the method has a parameter some other type (class) C2 that declares a method with a parameter  of type (class) C; or, transitively, a class Ck that declares a method with a parameter of type (class) C.  

 

Enter your definitions into the file analyzer.pl.   Load into SWI Prolog the file problem2.pl – which includes database.pl and analyzer.pl.   Proceed as follows.   

%  prolog problem2.pl     % this might vary with platform: Mac, Linux, Windows 

 

?- analyze. 

… prints out banner message …  

     ?- subclass(c, a). 

 ?- why(subclass(c, a)).  % ‘why’ provides an explanation … ?- cycle(a). 

?- why(cycle(a)).    % ‘why’ provides an explanation  

Note:  The why(G) predicate is in the included file explain.pl. Sample test queries and their output are given in the file transcript.

WHAT TO SUBMIT:   Make a directory called A3_UBITId  if working solo or a directory called A3_UBITId1_UBITId2 if working as a pair (give UBITId's in alphabetic order).    Place in this directory your completed A3_Problem2 directory.  Compress the top-level directory and submit it using the submit_cse505 command. 

 

 

 

SAMPLE TINY OOPL CLASSES: 

class a {   int x1, y1;   b z1;   int f(int x1, d y1);   void m2(d w1);   real m3(c z1); 

}  

class b extends a {   double w1;   int x1, x2;   c x3;   int f(int q1, d r1);   void m3(a z1); 

}  

class c extends b {   d z1, z2;   int f2(c q1, d r1);   void m2(d w2); 

} 

 

  

 
 

SAMPLE DATABASE RELATIONS:   

 db_class(a, 'Object'). db_class(b, a). db_class(c, b). 

   db_method(a, f, [int,d]-int). db_method(a, m2, [d]-void). db_method(a, m3, [c]-real). db_method(b, m3, [a]-void). db_method(b, f, [int,d]-int). db_method(c, f2, [c,d]-int). 

db_method(c, m2, [d]-void).   

 db_field(a, x1:int). db_field(a, y1:int). db_field(a, z1:b). 

db_field(b, w1:double). db_field(b, x1:int). db_field(b, x2:int). db_field(b, x3:c). db_field(c, z1:d). db_field(c, z2:d). 
      

End of Assignment 3 Problem 2