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:- object(sort(_Type)).
:- info([
author is 'Paulo Moura',
version is 1.0,
date is 2000/4/22,
comment is 'List sorting parameterized by the type of the list elements.',
parnames is ['Type'],
source is 'Example adopted from the SICStus Objects documentation.']).
:- uses(list).
:- calls(comparingp).
:- public(sort/2).
:- mode(sort(+list, -list), one).
:- info(sort/2, [
comment is 'Sorts a list in ascending order.',
argnames is ['List', 'Sorted']]).
:- private(partition/4).
:- mode(partition(+list, +nonvar, -list, -list), one).
:- info(partition/4, [
comment is 'List partition in two sub-lists using a pivot.',
argnames is ['List', 'Pivot', 'Lowers', 'Biggers']]).
sort([], []).
sort([P| L], S) :-
partition(L, P, Small, Large),
sort(Small, S0),
sort(Large, S1),
list::append(S0, [P| S1], S).
partition([], _, [], []).
partition([X| L1], P, Small, Large) :-
parameter(1, Type),
( Type::(X < P) ->
Small = [X| Small1], Large = Large1
; Small = Small1, Large = [X| Large1]
),
partition(L1, P, Small1, Large1).
:- end_object.
:- object(rational,
implements(comparingp)).
:- info([
author is 'Paulo Moura',
version is 1.0,
date is 2000/4/22,
comment is 'Implements comparison between rational numbers represented as Num/Den.']).
N1/D1 < N2/D2 :-
{N1*D2 < N2*D1}.
N1/D1 =< N2/D2 :-
{N1*D2 =< N2*D1}.
N1/D1 > N2/D2 :-
{N1*D2 > N2*D1}.
N1/D1 >= N2/D2 :-
{N1*D2 >= N2*D1}.
N1/D1 =:= N2/D2 :-
{N1*D2 =:= N2*D1}.
N1/D1 =\= N2/D2 :-
{N1*D2 =\= N2*D1}.
:- end_object.
:- object(colours,
implements(comparingp)).
:- info([
author is 'Paulo Moura',
version is 1.0,
date is 2000/4/22,
comment is 'Implements comparison between visible colors.']).
Colour1 < Colour2 :-
order(Colour1, N1),
order(Colour2, N2),
{N1 < N2}.
Colour1 =< Colour2 :-
order(Colour1, N1),
order(Colour2, N2),
{N1 =< N2}.
Colour1 > Colour2 :-
order(Colour1, N1),
order(Colour2, N2),
{N1 > N2}.
Colour1 >= Colour2 :-
order(Colour1, N1),
order(Colour2, N2),
{N1 >= N2}.
Colour1 =:= Colour2 :-
{Colour1 == Colour2}.
Colour1 =\= Colour2 :-
{Colour1 \== Colour2}.
order(red, 1).
order(orange, 2).
order(yellow, 3).
order(green, 4).
order(blue, 5).
order(indigo, 6).
order(violet, 7).
:- end_object.
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