arg: Add no_arg and get_arg helper functions.

The no_arg function in this patch is a no-op.  It will do something
useful in the followups.

The get_arg function simple checks the next position on the command
line exists and returns that argument or raises a Arg.Missing.

This patch should introduce no functional change, it is simply code
refactoring.

In particular, this should not change the treatment of Arg.current
(see: http://caml.inria.fr/mantis/view.php?id=5197#c11147)

1 files changed, 35 insertions, 29 deletions

diff --git a/stdlib/arg.ml b/stdlib/arg.ml
index d8f5ff5e27..76ad4791c8 100644
--- a/stdlib/arg.ml
+++ b/stdlib/arg.ml
@@ -146,69 +146,75 @@ let parse_argv_dynamic ?(current=current) argv speclist anonfun errmsg =
         try assoc3 s !speclist
         with Not_found -> stop (Unknown s)
       in
+      let no_arg () = () in
+      let get_arg () =
+        if !current + 1 < l then argv.(!current + 1)
+        else stop (Missing s)
+      in
+      let consume_arg () = incr current in
       begin try
         let rec treat_action = function
         | Unit f -> f ();
-        | Bool f when !current + 1 < l ->
-            let arg = argv.(!current + 1) in
+        | Bool f ->
+            let arg = get_arg () in
             begin match bool_of_string_opt arg with
             | None -> raise (Stop (Wrong (s, arg, "a boolean")))
             | Some s -> f s
             end;
-            incr current;
-        | Set r -> r := true;
-        | Clear r -> r := false;
-        | String f when !current + 1 < l ->
-            f argv.(!current + 1);
-            incr current;
-        | Symbol (symb, f) when !current + 1 < l ->
-            let arg = argv.(!current + 1) in
+            consume_arg ();
+        | Set r -> no_arg (); r := true;
+        | Clear r -> no_arg (); r := false;
+        | String f ->
+            let arg = get_arg () in
+            f arg;
+            consume_arg ();
+        | Symbol (symb, f) ->
+            let arg = get_arg () in
             if List.mem arg symb then begin
-              f argv.(!current + 1);
-              incr current;
+              f arg;
+              consume_arg ();
             end else begin
               raise (Stop (Wrong (s, arg, "one of: "
                                           ^ (make_symlist "" " " "" symb))))
             end
-        | Set_string r when !current + 1 < l ->
-            r := argv.(!current + 1);
-            incr current;
-        | Int f when !current + 1 < l ->
-            let arg = argv.(!current + 1) in
+        | Set_string r ->
+            r := get_arg ();
+            consume_arg ();
+        | Int f ->
+            let arg = get_arg () in
             begin match int_of_string_opt arg with
             | None -> raise (Stop (Wrong (s, arg, "an integer")))
             | Some x -> f x
             end;
-            incr current;
-        | Set_int r when !current + 1 < l ->
-            let arg = argv.(!current + 1) in
+            consume_arg ();
+        | Set_int r ->
+            let arg = get_arg () in
             begin match int_of_string_opt arg with
             | None -> raise (Stop (Wrong (s, arg, "an integer")))
             | Some x -> r := x
             end;
-            incr current;
-        | Float f when !current + 1 < l ->
-            let arg = argv.(!current + 1) in
+            consume_arg ();
+        | Float f ->
+            let arg = get_arg () in
             begin match float_of_string_opt arg with
             | None -> raise (Stop (Wrong (s, arg, "a float")))
             | Some x -> f x
             end;
-            incr current;
-        | Set_float r when !current + 1 < l ->
-            let arg = argv.(!current + 1) in
+            consume_arg ();
+        | Set_float r ->
+            let arg = get_arg () in
             begin match float_of_string_opt arg with
             | None -> raise (Stop (Wrong (s, arg, "a float")))
             | Some x -> r := x
             end;
-            incr current;
+            consume_arg ();
         | Tuple specs ->
             List.iter treat_action specs;
         | Rest f ->
             while !current < l - 1 do
               f argv.(!current + 1);
-              incr current;
+              consume_arg ();
             done;
-        | _ -> raise (Stop (Missing s))
         in
         treat_action action
       with Bad m -> stop (Message m);