mml.rb

# Attempt at a MML parser and player in Sonic Pi

define :mml do |txt, vol_scale=100|
  octave = 5
  length = 4
  txt = txt.downcase.gsub(/^mml@| |;$/, '').gsub(/#/, '+').gsub(/w/, 'r')
  with_bpm 120 do
    until txt.empty?
      r = txt.scan(/^(.)([+-]?)(\d*)(\.?)(.*)$/)
      cmd, opt, num, dot, txt = r[0]
      #print cmd, opt, num
      case cmd
      when 'o'
        if not num.empty? then
          octave = num.to_i
        end
      when 'l'
        if not num.empty? then
          length = num.to_i
        end
      when 't'
        if not num.empty? then
          use_bpm num.to_i
        end
      when 'v'
        if not num.empty? then
          set_volume! num.to_f / vol_scale
        end
      when '>'
        octave += 1
      when '<'
        octave -= 1
      when 'a'..'g', 'r'
        a = if opt == '+' then 's' elsif opt == '-' then 'b' else '' end
        n = cmd
        if n != 'r' then
          n += a + octave.to_s
        end
        t = (if dot.empty? then 4.0 else 6.0 end) / (if num.empty? then length else num.to_i end)
        r = txt.scan(/^(\^|&[a-gr][+-]?)(\d*)(\.?)(.*)$/)
        until r.empty?
          cmd, num, dot, txt = r[0]
          t += (if dot.empty? then 4.0 else 6.0 end) / (if num.empty? then length else num.to_i end)
          r = txt.scan(/^(\^|&[a-gr][+-]?)(\d*)(\.?)(.*)$/)
        end
        play_pattern_timed [n.to_sym], [t], release: t
      when 'n'
        n = num.to_i + 12
        t = (if dot.empty? then 4.0 else 6.0 end) / length
        play_pattern_timed [n], [t], release: t
      else
        print "Unrecognised:", cmd + opt + num + dot
      end
    end
  end
end