[Eva] add bindings operators for Bottom

src/kernel_services/abstract_interp/bottom.ml

@@ -25,16 +25,23 @@ module Type = struct
 
   type 'a or_bottom = [ `Value of 'a | `Bottom ]
 
-  (* This monad propagates the `Bottom value if needed. *)
   let (>>-) t f = match t with
     | `Bottom  -> `Bottom
     | `Value t -> f t
 
-  (* Use this monad if the following function returns a simple value. *)
   let (>>-:) t f = match t with
     | `Bottom  -> `Bottom
     | `Value t -> `Value (f t)
 
+  let zip x y =
+    match x, y with
+    | `Bottom, _ | _, `Bottom -> `Bottom
+    | `Value x, `Value y -> `Value (x,y)
+
+  let (let+) = (>>-:)
+  let (and+) = zip
+  let (let*) = (>>-)
+  let (and*) = zip
 end
 
 include Type

src/kernel_services/abstract_interp/bottom.mli

@@ -33,6 +33,13 @@ module Type : sig
   (** Use this monad if the following function returns a simple value. *)
   val (>>-:) : 'a or_bottom -> ('a -> 'b) -> 'b or_bottom
 
+  (* Binding operators, applicative syntax *)
+  val (let+) : 'a or_bottom -> ('a -> 'b) -> 'b or_bottom
+  val (and+) : 'a or_bottom -> 'b or_bottom -> ('a * 'b) or_bottom
+
+  (* Binding operators, monad syntax *)
+  val (let*) : 'a or_bottom -> ('a -> 'b or_bottom) -> 'b or_bottom
+  val (and*) : 'a or_bottom -> 'b or_bottom -> ('a * 'b) or_bottom
 end
 
 include module type of Type