more consistent procedural assignment support

src/Convert/AsgnOp.hs

@@ -32,6 +32,6 @@ convertStmt (For inits cc asgns stmt) =
         convertAsgn (lhs, AsgnOp op, expr) =
             (lhs, AsgnOpEq, BinOp op (lhsToExpr lhs) expr)
         convertAsgn other = other
-convertStmt (AsgnBlk (AsgnOp op) lhs expr) =
-    AsgnBlk AsgnOpEq lhs (BinOp op (lhsToExpr lhs) expr)
+convertStmt (Asgn (AsgnOp op) mt lhs expr) =
+    Asgn AsgnOpEq mt lhs (BinOp op (lhsToExpr lhs) expr)
 convertStmt other = other

src/Convert/BlockDecl.hs

@@ -47,4 +47,4 @@ splitDecl (Variable d t ident a (Just e)) =
 splitDecl other = (other, Nothing)
 
 asgnStmt :: (LHS, Expr) -> Stmt
-asgnStmt = uncurry $ AsgnBlk AsgnOpEq
+asgnStmt = uncurry $ Asgn AsgnOpEq Nothing

src/Convert/ForDecl.hs

@@ -80,7 +80,7 @@ splitDecl other =
     error $ "invalid for loop decl: " ++ show other
 
 asgnStmt :: (LHS, Expr) -> Stmt
-asgnStmt = uncurry $ AsgnBlk AsgnOpEq
+asgnStmt = uncurry $ Asgn AsgnOpEq Nothing
 
 dummyDecl :: Maybe Expr -> Decl
 dummyDecl = Variable Local (IntegerAtom TInteger Unspecified) "_sv2v_dummy" []

src/Convert/Jump.hs

@@ -101,7 +101,7 @@ addJumpStateDeclStmt stmt =
     where (decls, [stmt']) = addJumpStateDeclTF [] [stmt]
 
 removeJumpState :: Stmt -> Stmt
-removeJumpState (orig @ (AsgnBlk _ (LHSIdent ident) _)) =
+removeJumpState (orig @ (Asgn _ _ (LHSIdent ident) _)) =
     if ident == jumpState
         then Null
         else orig
@@ -298,4 +298,4 @@ assertMsg True _ = return ()
 assertMsg False msg = error msg
 
 asgn :: Identifier -> Expr -> Stmt
-asgn x e = AsgnBlk AsgnOpEq (LHSIdent x) e
+asgn x e = Asgn AsgnOpEq Nothing (LHSIdent x) e

src/Convert/Logic.hs

@@ -80,7 +80,7 @@ convertDescription ports orig =
         fixModuleItem (Assign Nothing lhs expr) =
             if Set.disjoint usedIdents origIdents
                 then Assign Nothing lhs expr
-                else AlwaysC AlwaysComb $ AsgnBlk AsgnOpEq lhs expr
+                else AlwaysC AlwaysComb $ Asgn AsgnOpEq Nothing lhs expr
             where
                 usedIdents = execWriter $ collectNestedLHSsM lhsIdents lhs
         -- rewrite port bindings to use temporary nets where necessary
@@ -109,7 +109,7 @@ convertDescription ports orig =
                         t = Net TWire Unspecified [(DimsFn FnBits $ Right expr, Number "1")]
                         items =
                             [ MIPackageItem $ Decl $ Variable Local t tmp [] Nothing
-                            , AlwaysC AlwaysComb $ AsgnBlk AsgnOpEq lhs tmpExpr]
+                            , AlwaysC AlwaysComb $ Asgn AsgnOpEq Nothing lhs tmpExpr]
                         lhs = case exprToLHS expr of
                             Just l -> l
                             Nothing ->

src/Convert/Stream.hs

@@ -36,7 +36,7 @@ streamerBlock chunk size asgn output input =
     , Variable Local (IntegerAtom TInteger Unspecified) bas [] Nothing
     ]
     [ For inits cmp incr stmt
-    , AsgnBlk AsgnOpEq (LHSIdent bas) (Ident idx)
+    , Asgn AsgnOpEq Nothing (LHSIdent bas) (Ident idx)
     , For inits cmp2 incr2 stmt2
     , asgn output (Ident out)
     ]
@@ -55,23 +55,21 @@ streamerBlock chunk size asgn output input =
         incr = [(LHSIdent idx, AsgnOp Add, chunk)]
         lhs = LHSRange (LHSIdent out) IndexedMinus (BinOp Sub hi (Ident idx), chunk)
         expr = Range (Ident inp) IndexedPlus (Ident idx, chunk)
-        stmt = AsgnBlk AsgnOpEq lhs expr
+        stmt = Asgn AsgnOpEq Nothing lhs expr
         -- final chunk loop
         cmp2 = BinOp Lt (Ident idx) (BinOp Sub size (Ident bas))
         incr2 = [(LHSIdent idx, AsgnOp Add, Number "1")]
         lhs2 = LHSBit (LHSIdent out) (Ident idx)
         expr2 = Bit (Ident inp) (BinOp Add (Ident idx) (Ident bas))
-        stmt2 = AsgnBlk AsgnOpEq lhs2 expr2
+        stmt2 = Asgn AsgnOpEq Nothing lhs2 expr2
 
 streamerBlockName :: Expr -> Expr -> Identifier
 streamerBlockName chunk size =
     "_sv2v_strm_" ++ shortHash (chunk, size)
 
 traverseStmtM :: Stmt -> Writer Funcs Stmt
-traverseStmtM (AsgnBlk op lhs expr) =
-    traverseAsgnM (lhs, expr) (AsgnBlk op)
-traverseStmtM (Asgn mt lhs expr) =
-    traverseAsgnM (lhs, expr) (Asgn mt)
+traverseStmtM (Asgn op mt lhs expr) =
+    traverseAsgnM (lhs, expr) (Asgn op mt)
 traverseStmtM other = return other
 
 traverseAsgnM :: (LHS, Expr) -> (LHS -> Expr -> Stmt) -> Writer Funcs Stmt

src/Convert/Traverse.hs

@@ -244,8 +244,7 @@ traverseSinglyNestedStmtsM fullMapper = cs
             caseStmts <- mapM fullMapper $ map snd cases
             let cases' = zip (map fst cases) caseStmts
             return $ Case u kw expr cases'
-        cs (AsgnBlk op lhs expr) = return $ AsgnBlk op lhs expr
-        cs (Asgn    mt lhs expr) = return $ Asgn    mt lhs expr
+        cs (Asgn op mt lhs expr) = return $ Asgn op mt lhs expr
         cs (For a b c stmt) = fullMapper stmt >>= return . For a b c
         cs (While   e stmt) = fullMapper stmt >>= return . While   e
         cs (RepeatL e stmt) = fullMapper stmt >>= return . RepeatL e
@@ -375,12 +374,12 @@ traverseStmtLHSsM mapper = stmtMapper
         stmtMapper (Timing (Event sense) stmt) = do
             sense' <- senseMapper sense
             return $ Timing (Event sense') stmt
-        stmtMapper (Asgn (Just (Event sense)) lhs expr) = do
+        stmtMapper (Asgn op (Just (Event sense)) lhs expr) = do
             lhs' <- fullMapper lhs
             sense' <- senseMapper sense
-            return $ Asgn (Just $ Event sense') lhs' expr
-        stmtMapper (AsgnBlk op lhs expr) = fullMapper lhs >>= \lhs' -> return $ AsgnBlk op lhs' expr
-        stmtMapper (Asgn    mt lhs expr) = fullMapper lhs >>= \lhs' -> return $ Asgn    mt lhs' expr
+            return $ Asgn op (Just $ Event sense') lhs' expr
+        stmtMapper (Asgn op mt lhs expr) =
+            fullMapper lhs >>= \lhs' -> return $ Asgn op mt lhs' expr
         stmtMapper (For inits me incrs stmt) = do
             inits' <- mapInits inits
             let (lhss, asgnOps, exprs) = unzip3 incrs
@@ -708,14 +707,10 @@ traverseStmtExprsM exprMapper = flatStmtMapper
         e' <- exprMapper e
         cases' <- mapM caseMapper cases
         return $ Case u kw e' cases'
-    flatStmtMapper (AsgnBlk op lhs expr) = do
+    flatStmtMapper (Asgn op mt lhs expr) = do
         lhs' <- lhsMapper lhs
         expr' <- exprMapper expr
-        return $ AsgnBlk op lhs' expr'
-    flatStmtMapper (Asgn    mt lhs expr) = do
-        lhs' <- lhsMapper lhs
-        expr' <- exprMapper expr
-        return $ Asgn    mt lhs' expr'
+        return $ Asgn op mt lhs' expr'
     flatStmtMapper (For inits cc asgns stmt) = do
         inits' <- initsMapper inits
         cc' <- exprMapper cc
@@ -1028,12 +1023,9 @@ collectAsgnsM = collectAsgnsM' IncludeTFs
 traverseStmtAsgnsM :: Monad m => MapperM m (LHS, Expr) -> MapperM m Stmt
 traverseStmtAsgnsM mapper = stmtMapper
     where
-        stmtMapper (AsgnBlk op lhs expr) = do
-            (lhs', expr') <- mapper (lhs, expr)
-            return $ AsgnBlk op lhs' expr'
-        stmtMapper (Asgn    mt lhs expr) = do
+        stmtMapper (Asgn op mt lhs expr) = do
             (lhs', expr') <- mapper (lhs, expr)
-            return $ Asgn    mt lhs' expr'
+            return $ Asgn op mt lhs' expr'
         stmtMapper other = return other
 
 traverseStmtAsgns :: Mapper (LHS, Expr) -> Mapper Stmt

src/Language/SystemVerilog/AST/Op.hs

@@ -100,11 +100,13 @@ instance Show BinOp where
 
 data AsgnOp
     = AsgnOpEq
+    | AsgnOpNonBlocking
     | AsgnOp BinOp
     deriving (Eq, Ord)
 
 instance Show AsgnOp where
     show AsgnOpEq = "="
+    show AsgnOpNonBlocking = "<="
     show (AsgnOp op) = (show op) ++ "="
 
 data StreamOp

src/Language/SystemVerilog/AST/Stmt.hs

@@ -38,8 +38,7 @@ data Stmt
     | Block   BlockKW Identifier [Decl] [Stmt]
     | Case    ViolationCheck CaseKW Expr [Case]
     | For     (Either [Decl] [(LHS, Expr)]) Expr [(LHS, AsgnOp, Expr)] Stmt
-    | AsgnBlk AsgnOp LHS Expr
-    | Asgn    (Maybe Timing) LHS Expr
+    | Asgn    AsgnOp (Maybe Timing) LHS Expr
     | While   Expr Stmt
     | RepeatL Expr Stmt
     | DoWhile Expr Stmt
@@ -83,8 +82,7 @@ instance Show Stmt where
             showAssign (l, op, e) = printf "%s %s %s" (show l) (show op) (show e)
     show (Subroutine e a) = printf "%s%s;" (show e) aStr
         where aStr = if a == Args [] [] then "" else show a
-    show (AsgnBlk o v e) = printf "%s %s %s;" (show v) (show o) (show e)
-    show (Asgn    t v e) = printf "%s <= %s%s;" (show v) (maybe "" showPad t) (show e)
+    show (Asgn  o t v e) = printf "%s %s %s%s;" (show v) (show o) (maybe "" showPad t) (show e)
     show (While   e s) = printf  "while (%s) %s" (show e) (show s)
     show (RepeatL e s) = printf "repeat (%s) %s" (show e) (show s)
     show (DoWhile e s) = printf "do %s while (%s);" (show s) (show e)
@@ -134,7 +132,6 @@ showElseBranch (stmt @ If{}) = ' ' : show stmt
 showElseBranch stmt = showBranch stmt
 
 showShortBranch :: Stmt -> String
-showShortBranch (stmt @ AsgnBlk{}) = ' ' : show stmt
 showShortBranch (stmt @ Asgn{}) = ' ' : show stmt
 showShortBranch stmt = showBranch stmt
 

src/Language/SystemVerilog/Parser/Parse.y

@@ -593,8 +593,8 @@ DeclTokens(delim) :: { [DeclToken] }
   : DeclToken                           delim  { [$1] }
   | DeclToken                DeclTokens(delim) { [$1] ++ $2 }
   | Identifier ParamBindings DeclTokens(delim) {% posInject \p -> [DTIdent p $1, DTParams p $2] ++ $3 }
-  | AsgnOp Expr ","          DeclTokens(delim) {% posInject \p -> [DTAsgn p $1 $2, DTComma p] ++ $4 }
-  | AsgnOp Expr                         delim  {% posInject \p -> [DTAsgn p $1 $2] }
+  | DeclTokenAsgn ","        DeclTokens(delim) {% posInject \p -> [$1, DTComma p] ++ $3 }
+  | DeclTokenAsgn                       delim  {% posInject \p -> [$1] }
 DeclToken :: { DeclToken }
   : ","                                {% posInject \p -> DTComma    p }
   | "[" "]"                            {% posInject \p -> DTAutoDim  p }
@@ -613,8 +613,11 @@ DeclToken :: { DeclToken }
   | "{" StreamOp StreamSize Concat "}" {% posInject \p -> DTStream   p $2 $3           (map toLHS $4) }
   | "{" StreamOp            Concat "}" {% posInject \p -> DTStream   p $2 (Number "1") (map toLHS $3) }
   | opt("var") "type" "(" Expr ")"     {% posInject \p -> DTType     p (\Unspecified -> \[] -> TypeOf $4) }
-  | "<=" opt(DelayOrEventControl) Expr {% posInject \p -> DTAsgnNBlk p $2 $3 }
-  | IncOrDecOperator                   {% posInject \p -> DTAsgn     p (AsgnOp $1) (Number "1") }
+  | "<=" opt(DelayOrEvent) Expr        {% posInject \p -> DTAsgn     p AsgnOpNonBlocking $2 $3 }
+  | IncOrDecOperator                   {% posInject \p -> DTAsgn     p (AsgnOp $1) Nothing (Number "1") }
+DeclTokenAsgn :: { DeclToken }
+  : "=" opt(DelayOrEvent) Expr {% posInject \p -> DTAsgn p AsgnOpEq $2 $3 }
+  | AsgnBinOp Expr             {% posInject \p -> DTAsgn p $1 Nothing $2 }
 
 VariablePortIdentifiers :: { [(Identifier, Maybe Expr)] }
   : VariablePortIdentifier                             { [$1] }
@@ -902,10 +905,11 @@ Stmt :: { Stmt }
   | StmtTrace StmtNonAsgn { $2 }
 
 StmtAsgn :: { Stmt }
-  : LHS AsgnOp Expr ";"                        { AsgnBlk $2 $1 $3 }
-  | LHS IncOrDecOperator ";"                   { AsgnBlk (AsgnOp $2) $1 (Number "1") }
-  | IncOrDecOperator LHS ";"                   { AsgnBlk (AsgnOp $1) $2 (Number "1") }
-  | LHS "<=" opt(DelayOrEventControl) Expr ";" { Asgn $3 $1 $4 }
+  : LHS "="  opt(DelayOrEvent) Expr ";" { Asgn AsgnOpEq $3 $1 $4 }
+  | LHS "<=" opt(DelayOrEvent) Expr ";" { Asgn AsgnOpNonBlocking $3 $1 $4 }
+  | LHS AsgnBinOp              Expr ";" { Asgn $2  Nothing $1 $3 }
+  | LHS IncOrDecOperator ";" { Asgn (AsgnOp $2) Nothing $1 (Number "1") }
+  | IncOrDecOperator LHS ";" { Asgn (AsgnOp $1) Nothing $2 (Number "1") }
   | LHS          ";" { Subroutine (lhsToExpr $1) (Args [] []) }
   | LHS CallArgs ";" { Subroutine (lhsToExpr $1) $2 }
 StmtNonAsgn :: { Stmt }
@@ -1007,9 +1011,9 @@ ClockingEvent :: { Sense }
   : "@" "(" Senses ")" { $3 }
 
 TimingControl :: { Timing }
-  : DelayOrEventControl { $1 }
+  : DelayOrEvent { $1 }
   | CycleDelay   { Cycle $1 }
-DelayOrEventControl :: { Timing }
+DelayOrEvent :: { Timing }
   : DelayControl { Delay $1 }
   | EventControl { Event $1 }
 DelayControl :: { Expr }
@@ -1237,7 +1241,9 @@ GenvarIteration :: { (Identifier, AsgnOp, Expr) }
 
 AsgnOp :: { AsgnOp }
   : "=" { AsgnOpEq }
-  | "+="   { AsgnOp Add }
+  | AsgnBinOp { $1 }
+AsgnBinOp :: { AsgnOp }
+  : "+="   { AsgnOp Add }
   | "-="   { AsgnOp Sub }
   | "*="   { AsgnOp Mul }
   | "/="   { AsgnOp Div }

src/Language/SystemVerilog/Parser/ParseDecl.hs

@@ -55,8 +55,7 @@ import Language.SystemVerilog.Parser.Tokens (Position(..))
 data DeclToken
     = DTComma    Position
     | DTAutoDim  Position
-    | DTAsgn     Position AsgnOp Expr
-    | DTAsgnNBlk Position (Maybe Timing) Expr
+    | DTAsgn     Position AsgnOp (Maybe Timing) Expr
     | DTRange    Position (PartSelectMode, Range)
     | DTIdent    Position Identifier
     | DTPSIdent  Position Identifier Identifier
@@ -73,9 +72,9 @@ data DeclToken
     deriving (Show, Eq)
 
 
--- entrypoints besides `parseDTsAsDeclOrStmt` use this to disallow `DTAsgnNBlk`
--- and `DTAsgn` with a binary assignment operator because we don't expect to see
--- those assignment operators in declarations
+-- entrypoints besides `parseDTsAsDeclOrStmt` use this to disallow `DTAsgn` with
+-- a non-blocking operator, binary assignment operator, or a timing control
+-- because we don't expect to see those assignment operators in declarations
 forbidNonEqAsgn :: [DeclToken] -> a -> a
 forbidNonEqAsgn tokens =
     if any isNonEqAsgn tokens
@@ -83,8 +82,8 @@ forbidNonEqAsgn tokens =
         else id
     where
         isNonEqAsgn :: DeclToken -> Bool
-        isNonEqAsgn (DTAsgnNBlk _ _ _) = True
-        isNonEqAsgn (DTAsgn _ (AsgnOp _) _) = True
+        isNonEqAsgn (DTAsgn _ op mt  _) =
+            op /= AsgnOpEq || mt /= Nothing
         isNonEqAsgn _ = False
 
 
@@ -211,8 +210,8 @@ parseDTsAsDecl tokens =
 parseDTsAsDeclOrStmt :: [DeclToken] -> ([Decl], [Stmt])
 parseDTsAsDeclOrStmt [DTIdent   pos   f] = ([], [traceStmt pos, Subroutine (Ident     f) (Args [] [])])
 parseDTsAsDeclOrStmt [DTPSIdent pos p f] = ([], [traceStmt pos, Subroutine (PSIdent p f) (Args [] [])])
-parseDTsAsDeclOrStmt (DTAsgn pos (AsgnOp op) e : tok : toks) =
-    parseDTsAsDeclOrStmt $ (tok : toks) ++ [DTAsgn pos (AsgnOp op) e]
+parseDTsAsDeclOrStmt (DTAsgn pos (AsgnOp op) mt e : tok : toks) =
+    parseDTsAsDeclOrStmt $ (tok : toks) ++ [DTAsgn pos (AsgnOp op) mt e]
 parseDTsAsDeclOrStmt tokens =
     if (isStmt (last tokens) || tripLookahead tokens) && maybeLhs /= Nothing
         then ([], [traceStmt pos, stmt])
@@ -220,14 +219,12 @@ parseDTsAsDeclOrStmt tokens =
     where
         pos = tokPos $ last tokens
         stmt = case last tokens of
-            DTAsgn     _ op e -> AsgnBlk op lhs e
-            DTAsgnNBlk _ mt e -> Asgn    mt lhs e
+            DTAsgn  _ op mt e -> Asgn op mt lhs e
             DTInstance _ args -> Subroutine (lhsToExpr lhs) (instanceToArgs args)
             _ -> error $ "invalid block item decl or stmt: " ++ (show tokens)
         maybeLhs = takeLHS $ init tokens
         Just lhs = maybeLhs
         isStmt :: DeclToken -> Bool
-        isStmt (DTAsgnNBlk{}) = True
         isStmt (DTAsgn{}) = True
         isStmt (DTInstance{}) = True
         isStmt _ = False
@@ -272,20 +269,19 @@ parseDTsAsAsgns tokens =
         lhs = case takeLHS lhsToks of
             Nothing -> error $ "could not parse as LHS: " ++ show lhsToks
             Just l -> l
-        DTAsgn _ AsgnOpEq expr : l1 = l0
+        DTAsgn _ AsgnOpEq Nothing expr : l1 = l0
         asgn = (lhs, expr)
 
         isDTAsgn :: DeclToken -> Bool
-        isDTAsgn (DTAsgn{}) = True
+        isDTAsgn (DTAsgn _ _ Nothing _) = True
         isDTAsgn _ = False
 
 isAsgnToken :: DeclToken -> Bool
-isAsgnToken (DTBit             _ _) = True
-isAsgnToken (DTConcat          _ _) = True
-isAsgnToken (DTStream      _ _ _ _) = True
-isAsgnToken (DTDot             _ _) = True
-isAsgnToken (DTAsgnNBlk      _ _ _) = True
-isAsgnToken (DTAsgn _ (AsgnOp _) _) = True
+isAsgnToken (DTBit{}   ) = True
+isAsgnToken (DTConcat{}) = True
+isAsgnToken (DTStream{}) = True
+isAsgnToken (DTDot{}   ) = True
+isAsgnToken (DTAsgn _ op _ _) = op /= AsgnOpEq
 isAsgnToken _ = False
 
 takeLHS :: [DeclToken] -> Maybe LHS
@@ -415,8 +411,8 @@ takeRanges (token : tokens) =
         DTBit   _ s               -> (asRange s : rs, rest          )
         DTAutoDim _               ->
             case rest of
-                (DTAsgn _ AsgnOpEq (Pattern l) : _) -> autoDim l
-                (DTAsgn _ AsgnOpEq (Concat  l) : _) -> autoDim l
+                (DTAsgn _ AsgnOpEq Nothing (Pattern l) : _) -> autoDim l
+                (DTAsgn _ AsgnOpEq Nothing (Concat  l) : _) -> autoDim l
                 _ ->                 ([]            , token : tokens)
         _                         -> ([]            , token : tokens)
     where
@@ -430,13 +426,15 @@ takeRanges (token : tokens) =
                 lo = Number "0"
                 hi = Number $ show (n - 1)
 
--- Matching DTAsgnNBlk here allows tripLookahead to work both for standard
--- declarations and in `parseDTsAsDeclOrStmt`, where we're checking for an
--- assignment statement. The other entry points disallow `DTAsgnNBlk`, so this
--- doesn't liberalize the parser.
+-- Matching `AsgnOpEq` and `AsgnOpNonBlocking` here allows tripLookahead to work
+-- both for standard declarations and in `parseDTsAsDeclOrStmt`, where we're
+-- checking for an assignment statement. The other entry points disallow
+-- `AsgnOpNonBlocking`, so this doesn't liberalize the parser.
 takeAsgn :: [DeclToken] -> (Maybe Expr, [DeclToken])
-takeAsgn (DTAsgn _ AsgnOpEq e : rest) = (Just e , rest)
-takeAsgn (DTAsgnNBlk    _ _ e : rest) = (Just e , rest)
+takeAsgn (DTAsgn _ op Nothing e : rest) =
+    if op == AsgnOpEq || op == AsgnOpNonBlocking
+        then (Just e , rest)
+        else (Nothing, rest)
 takeAsgn rest = (Nothing, rest)
 
 takeComma :: [DeclToken] -> (Bool, [DeclToken])
@@ -460,8 +458,7 @@ isComma _ = False
 tokPos :: DeclToken -> Position
 tokPos (DTComma    p) = p
 tokPos (DTAutoDim  p) = p
-tokPos (DTAsgn     p _ _) = p
-tokPos (DTAsgnNBlk p _ _) = p
+tokPos (DTAsgn     p _ _ _) = p
 tokPos (DTRange    p _) = p
 tokPos (DTIdent    p _) = p
 tokPos (DTPSIdent  p _ _) = p

test/basic/delay.sv

+module top;
+    logic [4] a, b;
+    always b = #5 a;
+    initial begin
+        a = #1 1;
+        $monitor("%2d %b %b", $time, a, b);
+        #1; a = 0;
+        #1; a = 'he;
+        #1;
+        #10; a = 'h5;
+        #10;
+        $finish;
+    end
+endmodule

test/basic/delay.v

+module top;
+    reg [0:3] a, b;
+    always b = #5 a;
+    initial begin
+        a = #1 1;
+        $monitor("%2d %b %b", $time, a, b);
+        #1; a = 0;
+        #1; a = 'he;
+        #1;
+        #10; a = 'h5;
+        #10;
+        $finish;
+    end
+endmodule