/**

Counter=2

?- trace,

chorussoloprogression('C','D').

[C, D]

Yes

Counter=3

?- chorussoloprogression('C','G').

[[C, D, G], [C, F, G]]

Yes

**/

chorussoloprogression(Name1, Name2) :-

note(Note1, Name1),

note(Note2, Name2),

chorussoloprogression(Note1, Note2, 0, _, [Note1], Progression1), notestonames(Progression1,Progression2), writeln(Progression2).

chorussoloprogression(_, _, Counter, b, Progression, Progression) :-

Counter = 5, !.

chorussoloprogression(Note, Note, _Counter, a, Progression, Progression) :- !.

chorussoloprogression(Note1, Note2, Counter1, Flag1, Progression1, Progression2) :-

Counter2 is Counter1 + 1,

step1(Note1, Note3),

append(Progression1, [Note3], Progression3),

chorussoloprogression(Note3, Note2, Counter2, Flag2, Progression3, Progression4),

step2(Note1, Note4),

append(Progression1, [Note4], Progression5),

chorussoloprogression(Note4, Note2, Counter2, Flag3, Progression5, Progression6),

flag(Flag2, Progression4, Flag3, Progression6, Flag1, Progression2).

step1(Note1, Note2) :-

Value is Note1+2, Note2 is Value mod 11.

step2(Note1, Note2) :-

Value is Note1+5, Note2 is Value mod 11.

notestonames(Progression1, Progression2) :-

notestonames1(Progression1, [], Progression2).

notestonames1([],P2,P2).

notestonames1([P|Progression1], Progression2, Progression3) :-

notestonames2(P, [], Progression4),

append(Progression2, [Progression4], Progression5),

notestonames1(Progression1, Progression5, Progression3).

notestonames2([], Progression2, Progression2).

notestonames2([P1|Progression1], Progression2, Progression3) :-

note(P1,Name),append(Progression2,[Name],Progression4),

notestonames2(Progression1, Progression4, Progression3).

flag(a,Progression1,a,Progression2,a,[Progression1,Progression2]) :- !.

flag(a,Progression1,_,_Progression2,a,Progression1) :- !.

flag(_,_Progression1,a,Progression2,a,Progression2) :- !.

flag(_,_,_,_,b,[]).

note(0,'C').

note(1,'C#').

note(2,'D').

note(3,'D#').

note(4,'E').

note(5,'F').

note(6,'F#').

note(7,'G').

note(8,'G#').

note(9,'A').

note(10,'A#').

note(11,'B').