P-99: Ninety-Nine Prolog Problems

p99.pl

% This is Prolog. This is not Perl.

:- module(p99, []).

% source:
% https://www.ic.unicamp.br/~meidanis/courses/mc336/2009s2/prolog/problemas/

% P01
last_of([X], X).
last_of([_|Rest], R) :-
    last_of(Rest, R).

% P03
kth_of([E|_], N, N, Out) :- Out = E.
kth_of([_|T], N, Current, Out) :-
    Current<N,
    C1 is Current+1,
    kth_of(T, N, C1, Out).

% P04
len_of([], Out) :- Out = 0.
len_of([_|T], Out) :-
    len_of(T, L1),
    Out is 1+L1.

% P05
rev_of([], Out) :- Out = [].
rev_of([H|T], Out) :-
    rev_of(T, R1),
    append(R1, [H], Out).

% P06
is_palindrome(L, Out) :-
    rev_of(L, L1),
    (L1 = L -> Out=true ; Out=false).

% P07
flatten_of([], Out) :- Out = [].
flatten_of([H|T], Out) :-
    (
        is_list(H) ->
        flatten_of(H, L1),
        flatten_of(T, L2),
        append(L1, L2, Out)
    ;
        flatten_of(T, L),
        append([H], L, Out)
    ).

% P08

no_duplicates([], []).
no_duplicates([E], Out) :- !, Out=[E].
no_duplicates([H,H|T], Out) :- !, no_duplicates([H|T], Out).
no_duplicates([H|T], [H|L1]) :- no_duplicates(T, L1).

:- begin_tests(test_suite).

test(last_of, all(Out = [d])) :-
    last_of([a,b,c,d], Out).

test(kth_of, all(Out = [c])) :-
    kth_of([a,b,c,d],3,1,Out).

test(len_of) :-
    len_of([a,b,c,d], 4),
    len_of([a,b,c], 3),
    len_of([], 0).

test(rev_of) :-
    rev_of([a,b,c], [c,b,a]),
    rev_of([a,b,c,d], [d,c,b,a]).

test(is_palindrome) :-
    is_palindrome([a,b,c,b,a], true).

test(is_palindrome) :-
    is_palindrome([a,b,d,d,d,a], false).

test(flatten_of) :-
    flatten_of([1,[2,3]], [1,2,3]),
    flatten_of([[1],[2,3]], [1,2,3]),
    flatten_of([[1],[2],[3]], [1,2,3]),
    flatten_of([[1,2],[3]], [1,2,3]),
    flatten_of([[1,2],3], [1,2,3]).

:- end_tests(test_suite).

:- begin_tests(no_duplicates).

test(1) :-
    no_duplicates([], []).

test(2) :-
    no_duplicates([1], [1]).

test(3) :-
    no_duplicates([1,2], [1,2]).

test(4) :-
    no_duplicates([1,1,1,2,2,2], [1,2]).

test(5) :-
    no_duplicates([a,a,a,a,b,c,c,a,a,d,e,e,e,e], [a,b,c,a,d,e]).

:- end_tests(no_duplicates).