Improvements around REPL

builtins.ml

@@ -133,24 +133,24 @@ let rec lisp_print sexp =
       Null -> ()
     | Cons (_) ->
         begin
-          Printf.printf "(" ;
+          print_string "(" ;
           lisp_print (car sexp) ;
           let rec loop s =
             match s with
                 Cons (_) ->
-                  Printf.printf " " ;
+                  print_string " " ;
                   lisp_print (car s) ;
                   loop (cdr s)
               | _ -> ()
           in
             loop (cdr sexp) ;
-            Printf.printf ")" ;
+            print_string ")" ;
         end
     | Atom (n) ->
-        Printf.printf "%s" n
+        print_string n
     | Lambda (largs, lsexp) ->
-        Printf.printf "#" ;
+        print_string "#" ;
         lisp_print largs ;
         lisp_print lsexp
     | _ ->
-        Printf.printf "Error."                                
+        print_string "Error."

main.ml

@@ -5,8 +5,6 @@ open Sexp
 let lisp_read inp =
   let lexbuf = Lexing.from_channel inp in
     Parser.main Lexer.token lexbuf
-
-
 
 let init_env () =
   let env = Symtab.create 32 in
@@ -31,12 +29,14 @@ let _ =
   let chin = stdin 
   in
     while true do
-      (try
-         Printf.printf "> " ;
-         lisp_print (eval (lisp_read chin) env) 
-       with
-           Parsing.Parse_error -> Printf.printf "Parser error" 
-         | Lexer.Eof -> exit 0);
-      Printf.printf "\n"            
+      try
+        print_string "> " ;
+        flush stdout ;
+        let sexp_eval = eval (lisp_read chin) env in
+          lisp_print sexp_eval ;
+          print_newline () ;
+      with
+          Parsing.Parse_error -> print_endline "Parse error"
+        | Lexer.Eof -> exit 0
     done