Refactor REPL

main.ml

@@ -1,31 +1,44 @@
 open Printf
 
+exception Reset_line (* used to indicate ^C is pressed *)
+
+let version = "%%VERSION%%"
+
 let error_to_string e =
   try raise e with
   | Parser.Expected t -> sprintf "expected %s" t
   | Parser.Unexpected_token t -> sprintf "unexpected token \"%s\"" t
-  | Failure f -> f
+  | Failure f -> sprintf "error on %s" f
   | Division_by_zero -> "cannot divide by zero"
   | _ -> raise e
 
 let print_error e =
   printf "error: %s\n" @@ error_to_string e
 
-(* simple REPL *)
-let rec repl () : unit =
+(* read-eval-print *) 
+let rep () : unit =
   printf "> ";
   let line = read_line () in
-  if line <> "quit" then begin
-    (try
-       line
-       |> Lex.tokenize
-       |> Parser.parse
-       |> Eval.eval
-       |> Ast.typ_to_string
-       |> printf "%s\n"
-     with
-     | e -> print_error e);
-    repl ()
-  end
+  if line = "quit" then raise Exit;
+  line
+  |> Lex.tokenize
+  |> Parser.parse
+  |> Eval.eval
+  |> Ast.typ_to_string
+  |> printf "%s\n"
 
-let () = repl ()
+let init_repl () =
+  let sigintf _ = raise Reset_line in
+  Sys.(set_signal sigint (Signal_handle sigintf))
+
+(* simple REPL with error handling *)
+let rec repl () : unit =
+  try rep (); repl () with
+  | Exit | End_of_file -> ()
+  | Reset_line -> printf "\n"; repl ()
+  | e -> print_error e; repl ()
+
+let () =
+  init_repl ();
+  printf "Configurable Evaluator %s\n" version; (* banner *)
+  repl ()