% INTRODUCTION

country(germany).

geolocation(X) :- country(X).


bigger(russia, germany).
bigger(germany, belgium).
bigger(A, B) :-
    bigger(A, C), bigger(C, B).


% LIST EXERCISES

firstelement([A|_], A).


lastelement([A], A).
lastelement([_|A], B) :-
    lastelement(A, B).


secondlast([H,_], H).
secondlast([_|A], B) :-
    secondlast(A, B).


second([], []).
second([A], [A]).
second([A,_|B], [A|Restlist]) :-
        second(B, Restlist).


prepend(A, B, [A|B]).


duplicate([], []).
duplicate([A], [A,A]).
duplicate([H|T], [H,H|T2]) :-
        duplicate(T, T2).


% INSERTION SORT

insert(Element, [], [Element]).

insert(Element, [Hs|Ts], [Element,Hs|Ts]):-
    Element =< Hs.

insert(Element, [Hs|Ts], [Hs|Tl]) :-
    Element >= Hs, 
    insert(Element, Ts, Tl).

inssort([], []).
inssort([H|T], Result) :-
            inssort(T, X),
            insert(H, X, Result).