/**
output from energy.pl
gives notes for local minima and maxima

878 -+ 
87678 --++

changes_to_music(Changes,Music) :-
        changes_to_music1(Changes,[],d,Music1),
        find_minima_and_maxima(Changes,Music1,Music).
**/

%% ?- changes_to_music([+,+,-,-],Music).
%% Music = [c, d, e, d, c] ;

%% changes_to_music(Changes,Music)
%% Changes - List of +'s or -'s, indicating whether a note should 
%%      go up or down from the last one, respectively.
%% Music - List of notes

changes_to_music(Changes,Music) :-
        changes_to_music1(Changes,[],c,Music).

%% changes_to_music1(Changes,Music1,Music2,Music3)
%% Changes - as for changes_to_music/2
%% Music1 - Current list of notes
%% Music2 - Next note
%% Music3 - List of notes

changes_to_music1([],Music,Music1,Music2) :-
        append(Music,[Music1],Music2).
changes_to_music1([+|Changes],Music1,Music2,Music3) :-
        music(Music2,Music4), 
        changes_to_music2(Music1,Music2,Changes,Music4,Music3).
changes_to_music1([-|Changes],Music1,Music2,Music3) :-
        music(Music4,Music2), 
        changes_to_music2(Music1,Music2,Changes,Music4,Music3).

%% changes_to_music2(Music1,Music2,Changes,Music3,Music4) 
%% Music1, Music2, Changes - as for changes_to_music1/4
%% Music3 - Next note
%% Music4 - List of notes

changes_to_music2(Music1,Music2,Changes,Music3,Music4) :-
        append(Music1,[Music2],Music5),
        changes_to_music1(Changes,Music5,Music3,Music4).

%% music(Note,NextNote)
%% Note - First note
%% NextNote - Note about the first note

music(b,c).
music(c,d).
music(d,e).
music(e,f).
music(f,g).
music(g,a).
music(a,b).

%% ?- find_minima_and_maxima([+,+,-,-], [c, d, e, d, c], Music).
%% Music = [c, e, c] ;

%% find_minima_and_maxima(Changes,Music1,Music2).
%% Changes - List of +'s or -'s, indicating whether a note should
%%      go up or down from the last one, respectively.
%% Music1 - List of notes
%% Music2 - List of notes which are minima and maxima of Music1

find_minima_and_maxima([Change1|Changes],[Note1,Note2|Music1],Music2) :-
	find_minima_and_maxima1(Changes,Music1,Change1,Note2,[Note1],Music2).

%% find_minima_and_maxima1(Changes,Music1,Change,Note2,Note1,Music2).
%% Changes - as for find_minima_and_maxima/3
%% Music1 - rest of music
%% Change - '+' - go up a note
%%          '-' - go down a note
%% Note2 - second note
%% Note1 - first note
%% Music2 - list of notes

find_minima_and_maxima1([],[],_,Note1,Music1,Music2) :-
	append(Music1,[Note1],Music2).
find_minima_and_maxima1([Change1|Changes],[Note1|Music1],Change1,_,Music2,Music3) :-
	find_minima_and_maxima1(Changes,Music1,Change1,Note1,Music2,Music3).
find_minima_and_maxima1([Change1|Changes],[Note1|Music1],Change2,Note2,Music2,Music3) :-
        not(Change1=Change2), append(Music2,[Note2],Music4),
        find_minima_and_maxima1(Changes,Music1,Change1,Note1,Music4,Music3).