domains

    list=symbol*

    
predicates

    len(list)
    findlen(list,integer)

    
clauses

    len(X):-
        findlen(X,Count),
        write("\nLength Of List : "),
        write(Count).
        
    findlen([],X):-
        X=0.
    
    findlen([X|Tail],Count):-
        findlen(Tail,Prev),
        Count = Prev + 1.
        

OUT PUT
=======


Goal: len([a,b,c,d,e])

Length Of List : 5

Yes