Utils: add a few primitives

src/lib_stdlib/option.ml

@@ -27,6 +27,10 @@ let unopt_map ~f ~default = function
   | None -> default
   | Some x -> f x
 
+let unopt_exn err = function
+  | Some x -> x
+  | _ -> raise err
+
 let first_some a b = match a, b with
   | None, None -> None
   | None, Some v -> Some v

src/lib_stdlib/option.mli

@@ -22,6 +22,9 @@ val unopt: default:'a -> 'a option -> 'a
 (** [unopt_map f d x] is [y] if [x] is [Some y], [d] if [x] is [None] **)
 val unopt_map: f:('a -> 'b) -> default:'b -> 'a option -> 'b
 
+(** [unopt_exn exn x] is [y] if [x] is [Some y], or raises [exn] if [x] is [None] *)
+val unopt_exn : exn -> 'a option -> 'a
+
 (** First input of form [Some x], or [None] if none **)
 val first_some: 'a option -> 'a option -> 'a option
 

src/lib_stdlib/tzList.ml

@@ -133,3 +133,11 @@ let select n l =
     | x :: xs -> loop (pred n) (x :: acc) xs
   in
   loop n [] l
+
+let shift = function
+  | [] -> []
+  | hd :: tl -> tl@[hd]
+
+let rec product a b = match a with
+  | [] -> []
+  | hd :: tl -> (List.map (fun x -> (hd , x)) b) @ product tl b

src/lib_stdlib/tzList.mli

@@ -13,6 +13,12 @@ val remove: int -> 'a list -> 'a list
 (** [repeat n x] is a list of [n] [x]'s **)
 val repeat: int -> 'a -> 'a list
 
+(** [shift (hd :: tl)] computes [tl @ [hd]] *)
+val shift : 'a list -> 'a list
+
+(** [product a b] computes the cartesian product of two lists [a] and [b]. *)
+val product : 'a list -> 'b list -> ('a * 'b) list
+
 (** [take_n n l] returns the [n] first elements of [l]. When [compare]
     is provided, it returns the [n] greatest element of [l]. *)
 val take_n: ?compare:('a -> 'a -> int) -> int -> 'a list -> 'a list