how to use the MML compiler framework

minimal.lua

-- MGCInts library
-- this imports most modules except those in util
local MGCInts = require "mgcints"

-- create a default engine with 4 channels
local engine = MGCInts.Default.Engine(4, "test driver")
local macros = engine:getCommandTable()
local builder = MGCInts.MML.CmdBuilder()

-- build some dummy commands
for k, v in pairs {C = 60, D = 62, E = 64, F = 65, G = 67, A = 69, B = 71} do
  local cmd = builder:setHandler(function (ch)
    ch:addChunk(("  Note: %d (%s)\n"):format(v, k))
  end):make()
  macros:addCommand(k, cmd)
  macros:addCommand(k:lower(), cmd)
end

-- volume command
builder:setTable(macros)
builder:setHandler(function (ch, v)
  ch:addChunk(("  Volume: %d\n"):format(v))
end):param "Uint8":optional "100":make "v"

-- channel header / footer
local ch_cls = engine:getChannelClass()
function ch_cls:before ()
  self:addChunk("Channel " .. self.id .. ": \n")
end
function ch_cls:after ()
  self:addChunk "End of data\n\n"
end

-- test inserter, we will use standard output
engine:setInserter(function (rom, song, track)
  rom:write("MGCInts test\nTrack: " .. track .. "\n\n")
  song:doAll(function (ch)
    rom:write(ch.stream:build())
  end)
end)

-- compile an MML string
local mmlstr = [[
!13 v 72
!2  v108
!4  v
!1 cd !23 eF
!1234 gAb
]]
MGCInts.Music.Compiler():processFile(engine, mmlstr, io.stdout, 1)

--[[ output
MGCInts test
Track: 1

Channel 1: 
  Volume: 72
  Note: 60 (C)
  Note: 62 (D)
  Note: 67 (G)
  Note: 69 (A)
  Note: 71 (B)
End of data

Channel 2: 
  Volume: 108
  Note: 64 (E)
  Note: 65 (F)
  Note: 67 (G)
  Note: 69 (A)
  Note: 71 (B)
End of data

Channel 3: 
  Volume: 72
  Note: 64 (E)
  Note: 65 (F)
  Note: 67 (G)
  Note: 69 (A)
  Note: 71 (B)
End of data

Channel 4: 
  Volume: 100
  Note: 67 (G)
  Note: 69 (A)
  Note: 71 (B)
End of data
]]