list - 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

我认为这可能很简单：

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

你在哪里使用它：

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

并给你

X = [1, 3].