Prolog list recursion, add elements in list

Question

I need to write a recursion in prolog, which adds elements of two lists. Let's say we have a list, A = [a,b,c], and B = [d,e,f] and the final list, R, should look like this: R = [a+d, b+e, c+f].

I came up only with this:

xxx([a], [b], [a+b]).
xxx([H1|T1], [H2|T2], W) :- xxx(T1, T2, W), .(H1+H2, W).

But it gives me uncaught exception: error(syntax_error('user_input:5 (char:15) expression or ] expected in list'),read_term/3). I also tried this:

xxx([a], [b], [a+b]).
xxx([H1|T1], [H2|T2], W) :- xxx(T1, T2, W), append(H1+H2, W, []).

With no success: uncaught exception: error(syntax_error('user_input:4 (char:16) expression or ] expected in list'),read_term/3)

Im using Gnu prolog (gprolog)

Note that the dot operator . for building lists is usually hidden; you need to do some "trick" to be able to use it. This is probably what is giving the syntax error. — Regis Alenda
– Regis Alenda, Commented Dec 19, 2016 at 23:26

false · Accepted Answer · 2016-12-20 08:42:43Z

3

xxx([], [], []).
xxx([E|Es], [F|Fs], [E+F|EFs]) :-
   xxx(E, F, EFs).

or

..., maplist(ex, Es, Fs, EFs), ...

ex(E, F, E+F).

or

..., maplist(\E^F^(E+F)^true, Es, Fs, EFs), ...

using library(lambda)

edited Dec 20, 2016 at 8:42

answered Dec 19, 2016 at 23:22

false

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