diff --git a/smtLib.cabal b/smtLib.cabal
--- a/smtLib.cabal
+++ b/smtLib.cabal
@@ -1,5 +1,5 @@
 Name:           smtLib
-Version:        1.0.7
+Version:        1.0.8
 License:        BSD3
 License-file:   LICENSE
 Author:         Iavor S. Diatchki
@@ -34,7 +34,7 @@
     SMTLib2.PP
 
   build-depends:
-    base   < 5,
+    base   >= 4.5 && < 5,
     pretty
 
 
diff --git a/src/SMTLib1/AST.hs b/src/SMTLib1/AST.hs
--- a/src/SMTLib1/AST.hs
+++ b/src/SMTLib1/AST.hs
@@ -8,22 +8,24 @@
 -- URL:
 -- http://goedel.cs.uiowa.edu/smtlib/papers/format-v1.2-r06.08.05.pdf
 
-{-# LANGUAGE OverloadedStrings, Safe #-}
+{-# LANGUAGE OverloadedStrings, Safe, DeriveDataTypeable #-}
 module SMTLib1.AST where
 
+import Data.Typeable
+import Data.Data
 import Data.String(IsString(..))
 
 newtype Name  = N String
-                deriving (Eq,Ord,Show)
+                deriving (Eq,Ord,Show,Data,Typeable)
 
 data Ident    = I Name [Integer]
-                deriving (Eq,Ord,Show)
+                deriving (Eq,Ord,Show,Data,Typeable)
 
 data Quant    = Exists | Forall
-                deriving (Eq,Ord,Show)
+                deriving (Eq,Ord,Show,Data,Typeable)
 
 data Conn     = Not | Implies | And | Or | Xor | Iff | IfThenElse
-                deriving (Eq,Ord,Show)
+                deriving (Eq,Ord,Show,Data,Typeable)
 
 data Formula  = FTrue
               | FFalse
@@ -34,40 +36,43 @@
               | Let Name Term Formula
               | FLet Name Formula Formula
               | FAnnot Formula [Annot]
-                deriving (Eq,Ord,Show)
+                deriving (Eq,Ord,Show,Data,Typeable)
 
 type Sort     = Ident
 
 data Binder   = Bind { bindVar :: Name, bindSort :: Sort }
-                deriving (Eq,Ord,Show)
+                deriving (Eq,Ord,Show,Data,Typeable)
 
 data Term     = Var Name
               | App Ident [Term]
               | Lit Literal
               | ITE Formula Term Term
               | TAnnot Term [Annot]
-                deriving (Eq,Ord,Show)
+                deriving (Eq,Ord,Show,Data,Typeable)
 
 data Literal  = LitNum Integer
               | LitFrac Rational
               | LitStr String
-                deriving (Eq,Ord,Show)
+                deriving (Eq,Ord,Show,Data,Typeable)
 
 data Annot    = Attr { attrName :: Name, attrVal :: Maybe String }
-                deriving (Eq,Ord,Show)
+                deriving (Eq,Ord,Show,Data,Typeable)
 
 data FunDecl  = FunDecl { funName   :: Ident
                         , funArgs   :: [Sort]
                         , funRes    :: Sort
                         , funAnnots :: [Annot]
                         }
+  deriving (Data,Typeable)
 
 data PredDecl = PredDecl { predName   :: Ident
                          , predArgs   :: [Sort]
                          , predAnnots :: [Annot]
                          }
+  deriving (Data,Typeable)
 
 data Status   = Sat | Unsat | Unknown
+  deriving (Data,Typeable)
 
 data Command
   = CmdLogic Ident
@@ -79,6 +84,7 @@
   | CmdExtraPreds [ PredDecl ]
   | CmdNotes String
   | CmdAnnot Annot
+  deriving (Data,Typeable)
 
 -- aka "benchmark"
 data Script = Script { scrName :: Ident, scrCommands :: [Command] }
diff --git a/src/SMTLib2/AST.hs b/src/SMTLib2/AST.hs
--- a/src/SMTLib2/AST.hs
+++ b/src/SMTLib2/AST.hs
@@ -8,45 +8,47 @@
 -- URL:
 -- http://goedel.cs.uiowa.edu/smtlib/papers/smt-lib-reference-v2.0-r10.12.21.pdf
 
-{-# LANGUAGE OverloadedStrings, Safe #-}
+{-# LANGUAGE OverloadedStrings, Safe, DeriveDataTypeable #-}
 module SMTLib2.AST where
 
+import Data.Typeable
+import Data.Data
 import Data.String(IsString(..))
 
 newtype Name  = N String
-                deriving (Eq,Ord,Show)
+                deriving (Eq,Ord,Show,Data,Typeable)
 
 data Ident    = I Name [Integer]
-                deriving (Eq,Ord,Show)
+                deriving (Eq,Ord,Show,Data,Typeable)
 
 data Quant    = Exists | Forall
-                deriving (Eq,Ord,Show)
+                deriving (Eq,Ord,Show,Data,Typeable)
 
 data Binder   = Bind { bindVar :: Name, bindType :: Type }
-                deriving (Eq,Ord,Show)
+                deriving (Eq,Ord,Show,Data,Typeable)
 
 data Defn     = Defn { defVar :: Name, defExpr :: Expr }
-                deriving (Eq,Ord,Show)
+                deriving (Eq,Ord,Show,Data,Typeable)
 
 data Literal  = LitBV Integer Integer   -- ^ value, width (in bits)
               | LitNum Integer
               | LitFrac Rational
               | LitStr String
-                deriving (Eq,Ord,Show)
+                deriving (Eq,Ord,Show,Data,Typeable)
 
 data Type     = TApp Ident [Type]
               | TVar Name
-                deriving (Eq,Ord,Show)
+                deriving (Eq,Ord,Show,Data,Typeable)
 
 data Expr     = Lit Literal
               | App Ident (Maybe Type) [Expr]
               | Quant Quant [Binder] Expr
               | Let [Defn] Expr
               | Annot Expr [Attr]
-                deriving (Eq,Ord,Show)
+                deriving (Eq,Ord,Show,Data,Typeable)
 
 data Attr     = Attr { attrName :: Name , attrVal :: Maybe AttrVal }
-                deriving (Eq,Ord,Show)
+                deriving (Eq,Ord,Show,Data,Typeable)
 
 type AttrVal  = Expr    -- A bit of an approximation....
 
@@ -64,6 +66,7 @@
   | OptRandomSeed Integer
   | OptVerbosity Integer
   | OptAttr Attr
+  deriving (Data,Typeable)
 
 data InfoFlag
   = InfoAllStatistics
@@ -74,6 +77,7 @@
   | InfoStatus
   | InfoReasonUnknown
   | InfoAttr Attr
+  deriving (Data,Typeable)
 
 data Command
   = CmdSetLogic Name
@@ -93,7 +97,9 @@
   | CmdGetUnsatCore
   | CmdGetInfo InfoFlag
   | CmdGetOption Name
+  | CmdComment String
   | CmdExit
+  deriving (Data,Typeable)
 
 newtype Script = Script [Command]
 
diff --git a/src/SMTLib2/PP.hs b/src/SMTLib2/PP.hs
--- a/src/SMTLib2/PP.hs
+++ b/src/SMTLib2/PP.hs
@@ -156,11 +156,13 @@
       CmdGetUnsatCore   -> one "get-unsat-core"
       CmdGetInfo i      -> std "get-info" i
       CmdGetOption n    -> std "get-option" n
+      CmdComment s      -> vcat (map comment (lines s))
       CmdExit           -> one "exit"
     where mk x d = parens (text x <+> d)
           one x   = mk x empty
           std x a = mk x (pp a)
           fun x y as d = mk x (pp y <+> parens (fsep (map pp as)) <+> d)
+          comment s = text ";" <+> text s
 
 instance PP Script where
   pp (Script cs) = vcat (map pp cs)