feat: simulation start

src/lib/common/monad.ml

@@ -0,0 +1,26 @@
+
+module type Monad = sig
+  type 'a t
+
+  val return : 'a -> 'a t
+  val bind   : 'a t -> ('a -> 'b t) -> 'b t
+end
+
+module type FullMonad = sig
+  type 'a t
+
+  val return : 'a -> 'a t
+  val bind   : 'a t -> ('a -> 'b t) -> 'b t
+  val (>>=)  : 'a t -> ('a -> 'b t) -> 'b t
+  val (let*) : 'a t -> ('a -> 'b t) -> 'b t
+  val join   : 'a t t -> 'a t
+end
+
+module Expand (M : Monad) = struct
+  include M
+
+  let (>>=)  = M.bind
+  let (let*) = M.bind
+  let join m = M.bind m (fun m -> m)
+end
+