Worked on synth.

src/Makefile

@@ -1,4 +1,4 @@
-SOURCES = extlib.ml stream.ml visu.ml note.ml MIDI.ml pattern.ml instrument.ml output.ml OSC.ml
+SOURCES = extlib.ml stream.ml operator.ml visu.ml note.ml MIDI.ml pattern.ml instrument.ml output.ml OSC.ml
 RESULT = msynth
 THREADS = yes
 ANNOTATE = true

src/operator.ml

@@ -0,0 +1,61 @@
+(** Operators a stream generators. They consist of two combined monads: one for
+    the state and one for streams (as in [Stream]). They should replace [Stream]
+    if they prove practicable as one could forsee compiling those. *)
+
+type 'a typ =
+  | Float : float typ
+  (* | Bool : bool kind *)
+  | Pair : ('a typ * 'b typ) -> ('a * 'b) typ
+
+(* existential type *)
+type types =
+  | Type : 'a typ -> types
+
+type 'a reference = 'a typ * int
+
+type 'a value =
+  | Unit : unit value
+  | Float : float -> float value
+  | Ref : 'a reference -> 'a reference value
+  | Get : 'a reference -> 'a value
+  | Set : 'a reference * 'a value -> unit value
+
+(** {2 The outer monad (which is roughly the indexed state monad) } *)
+
+(** State of an operator. *)
+type state =
+  {
+    cell : types array; (** all allocated cells *)
+  }
+
+(** The outer monad. *)
+type 'a t = state -> state * 'a value
+
+let return x : 'a t =
+  fun o -> o, x
+
+let bind f x : ('a -> 'b t) -> 'a t -> 'b t =
+  fun o -> f (x o) o
+
+let ( let+ ) x f = bind f x
+
+let alloc : 'a typ -> 'a value -> 'a reference t =
+  fun t i o ->
+  let cell = Array.append o.cell [|Type t|] in
+  let n = Array.length cell - 1 in
+  { o with cell }, Ref (t, n)
+
+let alloc_float = alloc Float
+
+let get : 'a reference -> 'a t =
+  fun r -> return (Get r)
+
+let set : 'a reference -> 'a value -> unit t =
+  fun r x -> return (Set (r, x))
+
+(** {2 The stream monad} *)
+
+type dt = float
+
+(** Pure streams. *)
+type 'a stream = dt -> 'a