CODEWITHSUNDEEP
prolog
Samuel B. T.
Samuel B. T.

Reputation: 35

How to append an element to each element of a list ? (Prolog)

I'll like to append an element to each element of a list. the element must be a list too.

Exemple :

A = [a,b,c]
B = [ele,ele2]

The result would be:

R = [[a,ele,ele2],[b,ele,ele2],[c,ele,ele2]]

I tried 

 maplist(custom_append,A,B,R).

But it returns false with 

custom_append(X,Y,[X|Y]).

How can I achieve this ?

Upvotes: 1

Views: 138

Answers (2)

Valera Grishin
Valera Grishin

Reputation: 441

The straightforward way would be like this:

append_list([], _, []).

append_list([A|As], B, [[A|B]|Cs]) :-
    append_list(As, B, Cs).

Don't even need to use maplist.

Upvotes: 0

willeM_ Van Onsem
willeM_ Van Onsem

Reputation: 476547

Note that B is not a list over which you want to iterate, you want to append an element of A to the same list B.

The easiest way to achieve this, is probably by swapping the order of the elements in the custom_append/3 to:

custom_append(Y, X, [X|Y]).

and then we can obtain this by using a maplist/3:

maplist(custom_append(B), A, R).

we thus already make something that behaves quite similar to partial application: we pass a functor custom_append(B), and Prolog will then make a call with custom_append(B, Ai, Ri) (Ai and Ri are here used to denote the elements of the lists A and R).

Upvotes: 1

Related Questions