Swi-Prolog - how to delete the second element (if exist) in a list?

Question

I need to write a program in swi-prolog that removes the second value of a list. thanks!

Answer 1

I think it could be as easy as:

remove2nd([], []).
remove2nd([X], [X]).
remove2nd([X, Y|Z], [X|Z]).

where you use it as:

remove2nd([1,2,3], X).

and gives you

X = [1, 3].