Reject programs with var initialized twice

src/config.ml

@@ -0,0 +1,4 @@
+(** Maximum Number of variabnles declared in a sngle node.
+    * This corresponds to the sum of the number of local, input and output
+    * variables. *)
+let maxvar = 100

src/main.ml

@@ -65,19 +65,21 @@ let _ =
   (** Main functionality below *)
   print_verbose "Parsing the source file...";
   let ast =
+    let inchan = open_in !source_file in
     try
       begin
-      let inchan = open_in !source_file in
       let res = Parser.main Lexer.token (Lexing.from_channel inchan) in
       close_in inchan; res
       end
     with
     | Lexer.Lexing_error s ->
-        (exit_error (Format.sprintf "Error code:\n\t%s\n\n" s); exit 0)
+        (close_in_noerr inchan;
+          exit_error (Format.sprintf "Error code:\n\t%s\n\n" s); exit 0)
     | Utils.MyParsingError (s, l) ->
       begin
+        close_in_noerr inchan;
         Format.printf "Syntax error at %a: %s\n\n"
-          Pp.pp_loc l s;
+          Pp.pp_loc (l, !source_file) s;
         exit 0
       end in
 

src/parser.mly

@@ -4,9 +4,9 @@
 
   let current_location () = symbol_start_pos (), symbol_end_pos ()
 
-  let defined_nodes : (ident, t_node) Hashtbl.t = Hashtbl.create 100
+  let defined_nodes : (ident, t_node) Hashtbl.t = Hashtbl.create Config.maxvar
 
-  let defined_vars : (ident, t_var) Hashtbl.t = Hashtbl.create 100
+  let defined_vars : (ident, t_var * bool) Hashtbl.t = Hashtbl.create Config.maxvar
 
   let fetch_node (n: ident) =
     match Hashtbl.find_opt defined_nodes n with
@@ -20,7 +20,19 @@
     | None ->
         raise (MyParsingError
                 ("The var "^n^" does not exist.", current_location()))
-    | Some var -> var
+    | Some (var, _) -> var
+
+  let fetch_var_def (n: ident) : t_var =
+    match Hashtbl.find_opt defined_vars n with
+    | None ->
+        raise (MyParsingError
+                ("The var "^n^" does not exist.", current_location()))
+    | Some (var, true) ->
+        raise (MyParsingError
+                ("The variable "^n^" is defined for the second time.",
+                current_location()))
+    | Some (var, false) ->
+        (Hashtbl.replace defined_vars n (var, true) ; var)
 
   let concat_varlist  (t1, e1) (t2, e2) = (t1 @ t2, e1 @ e2)
 
@@ -205,11 +217,14 @@ param:
       (list_repeat (List.length idents) typ,
       match typ with
       | TBool ->
-        List.map (fun s -> Hashtbl.add defined_vars s (BVar s); BVar s) idents
+        List.map (fun s ->
+          Hashtbl.add defined_vars s (BVar s, false); BVar s) idents
       | TReal ->
-        List.map (fun s -> Hashtbl.add defined_vars s (RVar s); RVar s) idents
+        List.map (fun s ->
+          Hashtbl.add defined_vars s (RVar s, false); RVar s) idents
       | TInt  ->
-        List.map (fun s -> Hashtbl.add defined_vars s (IVar s); IVar s) idents) }
+        List.map (fun s ->
+          Hashtbl.add defined_vars s (IVar s, false); IVar s) idents) }
 ;
 
 ident_comma_list:
@@ -233,12 +248,12 @@ equation:
 
 pattern:
   | IDENT
-    { let v = fetch_var $1 in (type_var v, [v]) }
+    { let v = fetch_var_def $1 in (type_var v, [v]) }
   | LPAREN ident_comma_list_patt RPAREN { $2 };
 
 ident_comma_list_patt:
-  | IDENT { make_ident (fetch_var $1) }
-  | IDENT COMMA ident_comma_list_patt { add_ident (fetch_var $1) $3 }
+  | IDENT { make_ident (fetch_var_def $1) }
+  | IDENT COMMA ident_comma_list_patt { add_ident (fetch_var_def $1) $3 }
 
 expr:
   /* Note: EQUAL does not follow the nomenclature CMP_, ... */

src/pp.ml

@@ -6,12 +6,25 @@ open Ast
   | TBool :: t -> Format.fprintf fmt "bool %a" debug_type_pp t
   | TReal :: t -> Format.fprintf fmt "real %a" debug_type_pp t
 
-let pp_loc fmt (start, stop) =
-  Lexing.(
-    Format.fprintf fmt "%s: <l: %d, c: %d> -- <l: %d, c: %d>"
-      start.pos_fname
-      start.pos_lnum start.pos_cnum
-      stop.pos_lnum stop.pos_cnum)
+let pp_loc fmt ((start, stop), file) =
+  let spos, epos = 
+    Lexing.(start.pos_cnum, stop.pos_cnum) in
+  let f = open_in file in
+  try
+    begin
+      let rec aux linenum curpos =
+        let line = input_line f in
+        let nextpos = curpos + (String.length line) + 1 in
+        if nextpos >= epos then
+          Format.fprintf fmt "<line %d: %s >" linenum line
+        else
+          aux (linenum + 1) nextpos
+        in
+      aux 1 0;
+      close_in f
+    end
+  with e ->
+    (close_in_noerr f; Format.fprintf fmt "???")
 
 let rec pp_varlist fmt : t_varlist -> unit = function
   | ([], []) -> ()