math.randomseed(os.time())

--output random # between 0 and 1
function random()
  local big = 10000000
  return math.random(0,big)/big
end

--object representing a single note
Note = {
  order = 0; note = " ";

  new = function(order, note)
    local n = {}
    n.order = order
    n.note = note
    n.get = Note.get
    return n
  end;

  get = function(self)
    print(self.order, self.note)
  end
}

--object containing list of notes, contains all 12 notes by default
NoteList = {
  Note.new(1, 'Ab');
  Note.new(2, 'A');
  Note.new(3, 'Bb');
  Note.new(4, 'B');
  Note.new(5, 'C');
  Note.new(6, 'Db');
  Note.new(7, 'D');
  Note.new(8, 'Eb');
  Note.new(9, 'E');
  Note.new(10, 'F');
  Note.new(11, 'Gb');
  Note.new(12, 'G');

  get = function(self)
    for i=1,#self do
      self[i]:get()
    end
  end;

  new = function(self)
    local n = {}
    for k,v in pairs(NoteList) do
      n[k] = v
    end
    return n
  end;

  --randomly select N notes from default NoteList, retaining original sort order
  randomlist = function(self, N)
    local copy = NoteList.new()

    --shuffle the note list by assigning random # and sorting by it
    for k,v in ipairs(copy) do
      copy[k].random = random()
    end
    table.sort(copy, function(k1, k2) return k1.random < k2.random end)

    --delete all but first N notes
    for i=#copy, 1, -1 do
      if i > N then
        copy[i] = nil
      end
    end

    --sort back into original order (by note name) and output
    table.sort(copy, function(k1, k2) return k1.order < k2.order end)
    return copy
  end;

  --output space-separated list of notes from object
  output_list = function(self)
    local output = ""
    for k,v in ipairs(self) do
      if k==1 then output = self[k].note
      else output = output .. " " .. self[k].note
      end
    end
    return output
  end
}

--generate [num] note lists each containing between [min] and [max] total notes
function generate_lists(num, min, max)
  for i=1,num do
    n = math.random(min, max)
    local a = NoteList:randomlist(n)
    print(a:output_list())
  end
end

generate_lists(50, 2, 5)

--[[
sample output:
Bb F Gb
Ab D E F G
A Eb F
Gb G
B D E Gb
Bb Db
Bb D
Ab C D E
B C Db Eb E
Db D E Gb G
A D Eb
Eb E
D G
A Eb Gb
B Eb E
B D
F Gb
Ab Bb F Gb
B F Gb
C Db Eb Gb
Bb C
Gb G
Ab A D E Gb
C Db Gb
A Bb Db F
Ab Bb B G
B D
Db G
Bb B E F
Ab D E Gb
Db Gb G
Db Gb
Ab C D F Gb
Ab E
A Db Gb
Bb Db Eb Gb
A G
A Bb D Eb G
Db F
B D Gb
B D E
C D Eb F G
B F Gb G
B C D G
C Db
A Gb
B Eb E Gb
Bb Db Gb
Ab C E G
Bb B D G
--]]