CODEWITHSUNDEEP
prolog
newlearner
newlearner

Reputation: 23

prolog-two lists, do the operation on the corresponding elements

I'm good at JAVA,now I'm learning Prolog,its so difficult that i need some help...thank you. each element of ABs is a term of the form A-B where A is the corresponding element of As and B is the corresponding element of Bs.

zip(As,Bs,ABs):

some examples:

zip([1,2,3,4],[a,b,c,d],L). 
  L=[1-a,2-b,3-c,4-d].

zip(X,Y,[1-a,2-b,3-c]).
  X=[1,2,3],Y=[a,b,c]
zip([1,2,3,4],[a,b,c],L). 
 fail.

can someone help me. thank you..

My implementation:

zip(As,Bs,ABs) :-
   append(X,XS,As),
   append(Y,YS,Bs),

this is what i have done..im lost..

Upvotes: 0

Views: 963

Answers (1)

coder
coder

Reputation: 12972

It is not very efficient to use append/3. You could simply write something like:

zip([],[],[]).
zip([H|T],[H1|T1],[H-H1|T2]):-zip(T,T1,T2).

Some examples:

?- zip([1,2,3,4],[a,b,c,d],L). 
L = [1-a, 2-b, 3-c, 4-d].

?- zip(X,Y,[1-a,2-b,3-c]).
X = [1, 2, 3],
Y = [a, b, c].

?- zip([1,2,3,4],[a,b,c],L). 
false.

Upvotes: 1

Related Questions