caml-urm

diff --git a/main.ml b/main.ml
@@ -1,74 +1,90 @@
 open List
 
-let usage = "USAGE: urm [-i ITERS] REGS FILE"
+let usage () = 
+  Printf.printf "USAGE: urm [-i ITERS] 'R0 R1 ...' FILE\n";
+  Printf.printf "See urm.1 for additional information\n"
 
 let default_max_iters = 1000
 
+(** An equivalent to Haskell's [sequence] *)
 let seq (xs : 'a option list) : 'a list option =
-  let f x acc = 
-    Option.join (Option.map (fun y -> Option.map (fun ys -> y :: ys) acc) x)
-  in List.fold_right f xs (Some [])
+    let f x acc = 
+        Option.join (Option.map (fun y -> Option.map (fun ys -> y :: ys) acc) x)
+    in List.fold_right f xs (Some [])
 
-let exec_file (iters : int) (regs : int array) (file : in_channel) : unit =
+
+(** Execute the program from [file] with initial register values given by
+    [regs] and the maximum number of allowed iterations set to [iters] *)
+let main iters regs file =
   let contents = really_input_string file (in_channel_length file) in
   try 
     let program = Urm.parse contents 
     and regs_fn = (fun i -> if i < Array.length regs then regs.(i) else 0) in
     match Urm.nexec iters program (Urm.of_registers regs_fn) with
     | Some m -> 
-        let final_regs = List.init (Array.length regs) (Urm.register m) in
-        Printf.printf "%s\n" 
-          (String.concat " " (map (Printf.sprintf "%d") final_regs))
+      let regs_strs = 
+        List.map 
+          (Printf.sprintf "%d") 
+          (List.init (Array.length regs) (Urm.register m))
+      in Printf.printf "%s\n" (String.concat " " regs_strs)
     | None -> 
-        Printf.eprintf 
-          "ERROR: the input program did not halt after %d iterations\n" 
-          iters;
-        Printf.eprintf "The input program may not halt\n";
-        exit 1
+      Printf.eprintf 
+        "ERROR: the input program did not halt after %d iterations\n" 
+        iters;
+      Printf.eprintf "The input program may not halt\n";
+      exit 1
   with Urm.Syntax_error err -> Printf.eprintf "ERROR: %s\n" err
 
 
-
+(** Initial parsing of the command-line arguments: get the strings out *)
 let (iters, regs_str, filepath) : int * string * string =
   let parse_iters iters_str =
     match int_of_string_opt iters_str with
     | Some n when n > 0 ->
-        n
+      n
     | Some n -> 
-        Printf.eprintf 
-          "ERROR: negative number of maximum iterations provided: %d\n" n;
-        Printf.eprintf "Expected a positive integers\n";
-        exit 1
+      Printf.eprintf 
+        "ERROR: negative number of maximum iterations provided: %d\n" n;
+      Printf.eprintf "Expected a positive integers\n";
+      usage ();
+      exit 1
     | None ->
-        Printf.eprintf 
-          "ERROR: invalid number of maximum iterations provided: '%s'\n" 
-          iters_str;
-        Printf.eprintf "Expected a positive integers\n";
-        exit 1
+      Printf.eprintf 
+        "ERROR: invalid number of maximum iterations provided: '%s'\n" 
+        iters_str;
+      Printf.eprintf "Expected a positive integers\n";
+      usage ();
+      exit 1
   in
     match Sys.argv with
     | [| _ ; "-i" ; iters_str ; regs ; filepath |] ->
-        (parse_iters iters_str, regs, filepath)
+      (parse_iters iters_str, regs, filepath)
     | [| _ ; regs ; filepath |] ->
-        (default_max_iters, regs, filepath)
+      (default_max_iters, regs, filepath)
     | argv when Array.length argv < 3 ->
       Printf.eprintf "ERROR: not enought arguments provided\n";
+      usage ();
       exit 1
     | _ -> 
       Printf.eprintf "ERROR: invalid arguments provided\n";
+      usage ();
       exit 1
 
+(** Parse the initial values of the registers as a list of ints separated by
+    spaces *)
 let regs =
   match seq (map int_of_string_opt (String.split_on_char ' ' regs_str)) with
   | Some regs ->
-      regs
+    regs
   | None ->
-      Printf.eprintf 
-        "ERROR: invalid initial values for the registers provided: '%s'\n"
-        regs_str;
-      Printf.eprintf "Expected a list of integers separated by spaces\n";
-      exit 1
+    Printf.eprintf 
+      "ERROR: invalid initial values for the registers provided: '%s'\n"
+      regs_str;
+    Printf.eprintf "Expected a list of integers separated by spaces\n";
+    usage ();
+    exit 1
 
+(** Try to open the file with the contents of the program *)
 let file =
   try
     open_in filepath
@@ -76,4 +92,5 @@ let file =
     Printf.eprintf "ERROR: %s\n" err;
     exit 1
 
-let () = exec_file iters (Array.of_list regs) file
+let () = main iters (Array.of_list regs) file
+