%% Measure distance the javelin is thrown

%% ?- distance([' ', ' ', ' ', '.'], Distance).

%% Distance = 3 ;

distance(Units, Distance) :-
	distance(Units, 0, Distance).
distance(['.'], Distance, Distance).
distance([' ' | Units], Distance1, Distance2) :-
	Distance3 is Distance1 + 1,
	distance(Units, Distance3, Distance2).

%% Objection: Lever breaks

%% ?- sound(strong, heavy, [[0, weak, light], [1, 'medium-strength', 'medium-weight'], [2, strong, heavy]], Sound).

%% Sound = 1 ;

sound(Strength, Weight, Thresholds, Sound) :-
	soundness1(Thresholds, Weight, Soundness1),
	soundness2(Thresholds, Strength, Soundness2),
	compare2(Soundness1, Soundness2, Sound).
soundness1(Thresholds, Weight, Soundness) :-
        member(Threshold, Thresholds),
        Threshold = [Soundness, _Strength, Weight].
soundness2(Thresholds, Strength, Soundness) :-
        member(Threshold, Thresholds),
        Threshold = [Soundness, Strength, _Weight].
compare2(Soundness1, Soundness2, 0) :-
        Soundness1 >= Soundness2.
compare2(Soundness1, Soundness2, 1) :-
        Soundness1 < Soundness2.