DonaldKellett

% set_accum/3 - A helper function using an acculumator to form a set from a given list
set_accum([H | T], Acc, Result) :- member(H, Acc), set_accum(T, Acc, Result).
set_accum([H | T], Acc, Result) :- \+ member(H, Acc), set_accum(T, [H | Acc], Result).
set_accum([], Acc, Acc).

% set/2 - Create a set of elements from a list
set(InList, OutList) :- set_accum(InList, [], Intermediate), reverse(Intermediate, OutList).

DonaldKellett

member(X, List) :- append(_, [X | _], List).

DonaldKellett

% Learn Prolog Now! - Chapter 6 - Exercise 6.6 - Who owns the zebra?
% A simplified version of Einstein's Riddle
% Problem Statement:
% There is a street with three neighboring houses that all have a different color, namely red, blue and green.  People of different nationalities live in the different houses and they all have a different pet.  Here are some more facts about them:
% - The Englishman lives in the red house
% - The jaguar is the pet of the Spanish family
% - The Japanese lives to the right of the snail keeper
% - The snail keeper lives to the left of the blue house
% Who keeps the zebra?  zebra/1 should tell us who this person is.

DonaldKellett

swapfl(List1, List2) :- append([A | M], [B], List1), append([B | M], [A], List2).

DonaldKellett

last([X], X).
last([_ | T], X) :- last(T, X).

DonaldKellett

last(List, X) :- reverse([X | _], List).

DonaldKellett

toptail([_ | T], OutList) :- append(OutList, [_], T).

DonaldKellett

palindrome(Result) :-
  append(L0, L1, Result), reverse(L0, L1);
  append(L0, [_ | L1], Result), reverse(L0, L1).

DonaldKellett

doubled(List) :- append(L, L, List).

DonaldKellett

dot([], [], 0).
dot([X | V1], [Y | V2], Z) :- dot(V1, V2, Result), Z is X * Y + Result.