:- object(driving,
extends(salesman)).
:- info([
author is 'Paulo Moura',
version is 1.0,
date is 2000/4/22,
comment is '.',
source is 'Example adopted from the Francis G. McCabe L&O documentation.']).
:- op(400, yfx, ~).
route(Towns, Route) :-
presort::route(Towns, Presort),
drive_around(Presort, Route).
drive_around(Route~Town1~Town2, Route1~Route2) :-
!,
drive_around(Route~Town1, Route1),
Town1::drive(Town2, Route2).
drive_around(Town1~Town2, Route) :-
Town1::drive(Town2, Route).
drive_around(Town, Town).
drive_length(Route, Length) :-
drive_length(Route, 0, Length).
drive_length(Route~Town1~Town2, Acc, Length) :-
Town1::road_distance(Town2, Length2),
Acc2 is Acc + Length2,
drive_length(Route~Town1, Acc2, Length).
drive_length(Town1~Town2, Acc, Length) :-
Length is Acc + Length2.
drive_length(_, Length, Length).
:- end_object.
