KNOWLEDGE MODELING AND REPRESENTATION - PROLOG

Prolog Programming.

(a) Find the last element in weekdays list.

            (i)      %  Find the last element in weekdays list .

% last(X, weekdays) ,  X is the last element of the list weekdays .

% (element, weekdays) (?,?) .

% Note : last(?element,? weekdays)

last(X,[X]).

last(X,[weekdays]).

X=Friday

 

(b) Find the N'th element in weekdays list. (N=2).

            (i)      % Find the N'th element of a list.

% The first element in the list is number 1.

% nth1(X, weekdays,N), X is the N'th element of the weekdays

% (nth1,list,integer) (?,?,+)

% Note to readers: nth1(?Index, ?List, ?element) is predefined.

nth1 (X,[X|_],1).

nth1(X,[_| weekdays], N),  N > 1, N1 is N - 1, nth1(X, weekdays, N1).

X=tuesday

   

(c) Reverse a list

(i)        % reverse(L1weekdays,L2weekdays) :- L2weekdays is the list obtained from L1weekdays by reversing the orders of the elements.

% (list,list) (?,?)

% Note : reverse(+List1weekdays, -List2weekdays) is predefined

reverse(L1weekdays,L2weekdays) , reverse (L1weekdays,L2weekdays,[]).

reverse ([],L2weekdays,L2weekdays) :- !.

reverse ([X|Xsenarai],L2weekdays,M),  reverse (Xsenarai,L2weekdays,[X|M]).

(d) Duplicate the elements in weekdays list.

(i)        % * Duplicate the elements in weekdays list * .

% dupli(X, weekdays) ,  X is the last element of the list weekdays .

% (element, weekdays) (?,?) .

% Note : dupli(?element,? weekdays)

dupli(X,[X]).

dupli(X,[weekdays]).

(f) Drop every N’th element from a weekdays list. (2nd element).

(i)        % drop(L1 weekdays,N,L2 weekdays) :- L2 weekdays is obtained from L1 weekdays by dropping every N'th element.

% (list,integer,list) (?,+,?)

drop(L1weekdays,N,L2weekdays) , drop(L1 weekdays, N, L2 weekdays, N).

% drop(L1 weekdays,N,L2 weekdays,N),  L2 weekdays is obtained from L1 weekdays by first copying N-1 elements

% and then dropping an element , dropping every

% N'th element.

% (list,integer,list,integer) (?,+,?,+)

drop([],_,[],_).

drop([_|Xweekdays],N,Yweekdays,1) :- drop(Xweekdays,N,Yweekdays,N).

drop([X|Xweekdays],N,[X|Yweekdays],K) :- N > 1, N1 is N - 1, drop(X weekdays,N,Yweekdays,N1).

(h) Rotate weekdays list N places to the left. (N=3)

(i) Remove the N'th element from a list. (2nd element)

(j) Extract a slice from a list.(position 2 and 4).