Assign **=.

src/Data/Syntax/Expression.hs

@@ -41,3 +41,10 @@ data Times a = Times a a
 
 instance Eq1 Times where liftEq = genericLiftEq
 instance Show1 Times where liftShowsPrec = genericLiftShowsPrec
+
+-- | Binary exponentiation.
+data Power a = Power a a
+  deriving (Eq, Foldable, Functor, Generic1, Show, Traversable)
+
+instance Eq1 Power where liftEq = genericLiftEq
+instance Show1 Power where liftShowsPrec = genericLiftShowsPrec

src/Language/Ruby/Syntax.hs

@@ -27,6 +27,7 @@ type Syntax' =
   , Expression.Not
   , Expression.Plus
   , Expression.Times
+  , Expression.Power
   , Literal.Array
   , Literal.Boolean
   , Literal.Hash
@@ -89,7 +90,8 @@ statement  =  exit Statement.Return Return
           <|> symbol OperatorAssignment *> term <*> children (lvalue >>= \ var -> Statement.Assignment var <$>
                (symbol AnonPlusEqual     *> term <*>  (Expression.Plus var <$> expression)
             <|> symbol AnonMinusEqual    *> term <*> (Expression.Minus var <$> expression)
-            <|> symbol AnonStarEqual  *> term <*> (Expression.Times var <$> expression)))
+            <|> symbol AnonStarEqual     *> term <*> (Expression.Times var <$> expression)
+            <|> symbol AnonStarStarEqual *> term <*> (Expression.Power var <$> expression)))
   where exit construct sym = symbol sym *> term <*> children (construct <$> optional (symbol ArgumentList *> children statement))
 
 lvalue :: Assignment (Node Grammar) (Term Syntax Location)