camlspotter avatar camlspotter committed f2b4e7f

Added Option.catch and Result.catch (and catch_exn)

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Files changed (4)

 let default v df = match v with
   | None -> df ()
   | Some v -> v
+
+let catch f =
+  let module Error = struct exception Error end in
+  let fail () = raise Error.Error in
+  try Some (f ~fail) with Error.Error -> None
+
+let catch_exn f = catch (fun ~fail -> try f () with _ -> fail ())
     but as a thunk [(unit -> 'a)], since such a value need to be created
     dynamically.
 *)
+
+val catch : (fail:(unit -> 'exn) -> 'a) -> 'a option
+val catch_exn : (unit -> 'a) -> 'a option
+type ('a, 'error) t = [`Ok of 'a | `Error of 'error]
+
+let catch f = 
+  let module Error = struct exception Error end in
+  let error = ref None in
+  let fail e = error := Some e; raise Error.Error in
+  try `Ok (f ~fail) with
+  | Error.Error -> 
+      match !error with
+      | Some e -> `Error e
+      | None -> assert false
+
+let catch_exn f = catch (fun ~fail -> try f () with e -> fail e)
+  
+type ('a, 'error) t = [`Ok of 'a | `Error of 'error]
+
+val catch : (fail:('error -> 'exn) -> 'a) -> [> ('a, 'error) t]
+(** [catch f] runs [f ~fail]. 
+
+    If [f ~fail] returns a value [v] then [catch f] returns [`Ok v].
+
+    If [f ~fail] calls [fail e], then the execution of the [f ~fail] immediately
+    exists and [catch f] returns [`Error e]
+
+    Any exception raised in [f ~fail] is not caught.
+*)
+
+val catch_exn : (unit -> 'a) -> [> `Error of exn | `Ok of 'a ]
+(** [catch_exn f] runs [f ()]. 
+
+    If [f ()] returns a value [v] then [catch f] returns [`Ok v].
+
+    If an exception [exn] raised in [f ()], [catch f] returns [`Error exn].
+*)
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