% The possible suspects of the crimes are:
possible_suspect(fred).
possible_suspect(mary).
possible_suspect(jane).
possible_suspect(george).
% The facts about the crimes from the police log.
crime(robbery1, john, tuesday, park).
crime(assault1, mary, wednesday, park).
crime(robbery2, jim, wednesday, pub).
crime(assault2, robin, thursday, park).
% Tell prolog where the suspects were on
% different days.
was_at(fred, park, tuesday).
was_at(fred, pub, wednesday).
was_at(fred, pub, thursday).
was_at(george, pub, tuesday).
was_at(george, pub, wednesday).
was_at(george, home, thursday).
was_at(jane, home, tuesday).
was_at(jane, park, wednesday).
was_at(jane, park, thursday).
was_at(mary, pub, tuesday).
was_at(mary, park, wednesday).
was_at(mary, home, thursday).
% Tell prolog who is jealous of who
jealous_of(fred, john).
jealous_of(jane, mary).
% And who owes money to whom
owes_money_to(george, jim).
owes_money_to(mary, robin).
% A Person has a motive against a Victim if
% Person is jealous of Victim or
% Person owes money to Victim
motive_against(Person, Victim) :-
jealous_of(Person, Victim);
owes_money_to(Person, Victim).
% A Person is a prime suspect of a crime if
% Person is a possible suspect and the person
% was at the time and place of the crime and
% the person had a motive against the victim
% of the crime.
prime_suspect(Person, Crime) :-
possible_suspect(Person),
was_at(Person, Place, Day),
crime(Crime, Victim, Day, Place),
motive_against(Person, Victim).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% QUERIES / RESPONSES FOR Q1
%
% 1 ?- prime_suspect(fred,robbery1).
%
% Yes
% 2 ?- prime_suspect(george, assault2).
%
% No
% 3 ?- prime_suspect(Prime_Suspect, robbery1).
%
% Prime_Suspect = fred ;
%
% No
% 4 ?- prime_suspect(Prime_Suspect, robbery2).
%
% Prime_Suspect = george ;
%
% No
% 5 ?- prime_suspect(Prime_Suspect, assault1).
%
% Prime_Suspect = jane ;
%
% No
% 6 ?- prime_suspect(Prime_Suspect, assault2).
%
% No
% 7 ?- prime_suspect(fred, Crime).
%
% Crime = robbery1 ;
%
% No
% 8 ?- prime_suspect(george, Crime).
%
% Crime = robbery2 ;
%
% No
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Q2. MISC %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% 1. Compute the last member of a nonempty list
last([X],X).
last([_|T],X) :-
last(T,X).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% 2. Reverse a list
append([],L,L).
append([H|T],L2,[H|L3]) :-
append(T,L2,L3).
reverse([],[]).
reverse([H|T],R) :-
reverse(T,X),
append(X,[H],R).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% 3. Remove one occurrence of X from list K
select(X,K,L) :-
append(I,[X|J],K),
append(I,J,L).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% 4. X and Y are different members of L
member(X,[X|_]).
member(X,[_|Yt]) :-
member(X,Yt).
% X and Y are different members of L if
% X is a member of L and Y is a member of
% list K where K is list L with X removed.
different(X,Y,L) :-
member(X,L),
select(X,L,K),
member(Y,K).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% 5. K and L are lists of the same length if
% they are both empty after chopping their
% heads off the same amount of times.
samelength([],[]).
samelength([_|K],[_|L]) :-
samelength(K,L).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% 6. K and L are lists of the same length and
% contain the same elements.
same_elements([],[]).
same_elements([Kh|Kt],L) :-
select(Kh,L,X),
same_elements(Kt,X).
% List K is similar to list L if
% K and L are the same length and
% K and L contain the same elements
similar([],[]).
similar(K, L) :-
samelength(K,L),
same_elements(K,L).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% QUERIES / RESPONSES FOR Q2
%
% 2 ?- last([a,b,c,d],Last).
%
% Last = d ;%
%
% No
% 3 ?- reverse([a,b,c,d],Reversed).
%
% Reversed = [d, c, b, a] ;
%
% No
% 4 ?- select(a,[a,b,c,a],List).
%
% List = [b, c, a] ;
%
% List = [a, b, c] ;
%
% No
% 5 ?- different(X,Y,[1,2,3]).
%
% X = 1
% Y = 2 ;
%
% X = 1
% Y = 3 ;
%
% X = 2
% Y = 1 ;
%
% X = 2
% Y = 3 ;
%
% X = 3
% Y = 1 ;
%
% X = 3
% Y = 2 ;
%
% No
% 6 ?- samelength([a,b,c],L).
%
% L = [_G359, _G362, _G365] ;
%
% No
% 7 ?- samelength(L,[a,b,c]).
%
% L = [_G359, _G362, _G365] ;
%
% No
% 8 ?- similar([a,b,a],L).
%
% L = [a, b, a] ;
%
% L = [a, a, b] ;
%
% L = [b, a, a] ;
%
% L = [a, a, b] ;
%
% L = [b, a, a] ;
%
% L = [a, b, a] ;
%
% No
% 9 ?- similar(L,[a,b,a]).
%
% L = [a, b, a] ;
%
% L = [a, a, b] ;
%
% L = [b, a, a] ;
%
% L = [b, a, a] ;
%
% L = [a, a, b] ;
%
% L = [a, b, a] ;
%
% No
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
