add amount compare

src/amount.ml

@@ -47,6 +47,14 @@ let make ~sign ~currency ~value ~fraction =
   let currency = String.uppercase_ascii currency in
   Ok { sign; currency; value; fraction }
 
+let compare a b =
+  match String.equal a.currency b.currency with
+  | false -> Fmt.failwith "amount compare on different currencies"
+  | true -> (
+      match Int64.unsigned_compare a.value b.value with
+      | 0 -> Int32.unsigned_compare a.fraction b.fraction
+      | n -> n)
+
 module Parser = struct
   open Angstrom
 

src/amount.mli

@@ -16,6 +16,8 @@ val make :
   fraction:Int32.t ->
   (t, string) result
 
+(* fail on differents currencies *)
+val compare : t -> t -> int
 val pp : Format.formatter -> t -> unit
 val to_string : t -> string
 val of_string : string -> (t, string) result

src/denomination.ml

@@ -99,16 +99,7 @@ let make_denom_group_sorted denominations =
   let open RsaDenomGroup in
   let open RsaDenom in
   let cmp_denom b a = Timestamp.compare a.stamp_start b.stamp_start in
-  let cmp_group =
-    let cmp_amount a b =
-      (* TODO amount *)
-      let open Amount in
-      match Int64.unsigned_compare a.value b.value with
-      | 0 -> Int32.unsigned_compare a.fraction b.fraction
-      | n -> n
-    in
-    fun (Rsa a) (Rsa b) -> cmp_amount a.value b.value
-  in
+  let cmp_group = fun (Rsa a) (Rsa b) -> Amount.compare a.value b.value in
   let l =
     l
     |> List.map