1 files changed, 153 insertions, 0 deletions
diff --git a/abstract/_constant_domain.ml b/abstract/_constant_domain.ml
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+++ b/abstract/_constant_domain.ml
@@ -0,0 +1,153 @@
+open Util
+open Abstract_syntax_tree
+
+module CD : Domain.S =
+  struct
+
+    exception DivideByZero
+    exception TypeError
+    exception Bot
+    exception NotImplemented
+
+    type tv =   (* type for a variable *)
+      | Top
+      | I of Z.t
+
+    type ts =   (* type for an environment *)
+      | Bot
+      | Nb of tv VarMap.t
+
+    let top_ts = Nb VarMap.empty
+
+    let ts_union a b =
+      begin match a, b with
+      | Bot, Bot -> Bot
+      | Nb a, Bot -> Nb a
+      | Bot, Nb b -> Nb b
+      | Nb a, Nb b ->
+        Nb
+          (VarMap.fold
+            (fun var value a ->
+              try match VarMap.find var a with
+                | Top -> a
+                | I x ->
+                  match value with
+                  | I y when y = x -> a
+                  | _ -> VarMap.add var Top a
+              with
+              | Not_found -> VarMap.add var value a)
+          b a)
+      end
+
+    (* must not raise exception *)
+    let ts_add_bool_constraint expr (s : ts) =
+      s (* TODO, not necessary... *)
+
+
+    (* only evaluates numerical statements, raises
+      TypeError when result is bool *)
+    let rec eval_abs expr (s : tv VarMap.t) =
+      match expr with
+      | AST_unary(op, (i, _)) ->
+        begin match eval_abs i s with
+        | Top -> Top
+        | I x ->
+          match op with
+          | AST_UNARY_PLUS -> I x
+          | AST_UNARY_MINUS -> I (Z.neg x)
+          | _ -> raise TypeError
+        end
+      | AST_binary(op, (a, _), (b, _)) ->
+        begin match eval_abs a s, eval_abs b s with
+        | I x, I  y ->
+          begin match op with
+          | AST_PLUS -> I (Z.add x y)
+          | AST_MINUS -> I (Z.sub x y)
+          | AST_MULTIPLY -> I (Z.mul x y)
+          | AST_DIVIDE ->
+            if y = Z.zero then raise DivideByZero;
+            I (Z.div x y)
+          | AST_MODULO ->
+            if y = Z.zero then raise DivideByZero;
+            I (Z.rem x y)
+          | _ -> raise TypeError
+          end
+        | _ -> Top
+        end
+      | AST_identifier(id, _) ->
+        begin
+          try VarMap.find id s
+          with _ -> Top
+        end 
+      | AST_int_const(s, _) ->
+        I (Z.of_string s)
+      | AST_bool_const(_) -> raise TypeError
+      | AST_int_rand _ -> Top
+      | _ -> raise NotImplemented (* extensions *)
+
+    (* returns true if the expression can evaluate to true
+      returns false if the expression always evaluates to false *)
+    let rec eval_bool_abs expr (s : tv VarMap.t) =
+      true (* TODO *)
+
+    (* must not raise exception *)
+    let rec interp_abs stat s =
+      begin match s with
+      | Bot -> Bot
+      | Nb vars ->
+        begin match stat with
+        | AST_block b ->
+          List.fold_left
+            (fun ss (st, _) -> interp_abs st ss)
+            s b
+        | AST_assign ((id, _), (exp, _)) ->
+          begin
+            try
+              let value = eval_abs exp vars in
+              Nb (VarMap.add id value vars)
+            with _ -> Bot
+          end
+        | AST_if ((cond, _), (tb, _), None) ->
+          ts_union (Nb vars)
+            (interp_abs tb
+              (ts_add_bool_constraint cond (Nb vars)))
+        | AST_if ((cond, l), (tb, _), Some (eb, _)) ->
+          ts_union
+            (interp_abs tb
+              (ts_add_bool_constraint cond (Nb vars)))
+            (interp_abs eb
+              (ts_add_bool_constraint 
+                  (AST_unary (AST_NOT, (cond, l)))
+                (Nb vars)))
+        | AST_while ((cond, _), (body, _)) ->
+          let f s =
+            ts_union
+              s
+              (ts_add_bool_constraint cond s)
+          in
+            fix f (Nb vars)
+        | AST_HALT -> Bot
+        | AST_assert (cond, _) ->
+          if eval_bool_abs cond vars
+            then Nb vars
+            else begin
+              print_string "Assert fail\n";
+              Bot
+            end
+        | AST_print items ->
+          List.iter
+            (fun (var, _) ->
+              print_string (var ^ " = ");
+              try
+                match VarMap.find var vars with
+                | Top -> print_string "T\n"
+                | I x -> print_string (Z.to_string x ^ "\n")
+              with _ -> print_string "T\n")
+            items;
+          Nb vars
+        | _ -> raise NotImplemented (* extensions *)
+        end
+      end
+
+  end
+