How to get the first, middle and last element of a list scheme and prolog?

Question

I am trying to write a function in Scheme and Prolog that returns first, middle and last item of a list. E.g., find([4,5,8,7,9],L), L = [4,8,9].

I came up w

Answer 1

Assuming that in the case that the list has even number of items you can choose one of them (in this case the first one), this procedure should work:

Edited per comment from user 'repeat' (i am not versed on Scheme)

find([First|List], [First, Middle, Last]):-
  append(_, [Last], [First|List]),
  length(List, Length),
  NLength is Length >> 1,
  nth0(NLength, [First|List], Middle).

The head of the clause instantiates the First item of the list, then append/3 takes the Last item, length/2 computes the size-1 of the list, >>/2 will divide that size by 2, and nth0/3 will get the Middle item.