diff --git a/ChristmasTree.cabal b/ChristmasTree.cabal
--- a/ChristmasTree.cabal
+++ b/ChristmasTree.cabal
@@ -1,7 +1,7 @@
-cabal-version:      >=1.2.3
+cabal-version:      >=1.2.3.1
 build-type:         Simple
 name:               ChristmasTree
-version:            0.2.1
+version:            0.2.1.1
 license:            LGPL
 license-file:       COPYRIGHT
 maintainer:         Marcos Viera <mviera@fing.edu.uy>
@@ -11,16 +11,22 @@
 category:           Parsing 
 stability:          Experimental
 copyright:          Universiteit Utrecht
-build-depends:      base >= 4 && < 5, haskell98, template-haskell >= 2.4, containers,
-                    fgl == 5.4.2.2, TTTAS >= 0.4 , uulib >= 0.9.11 
-exposed-modules:    Text.GRead, Text.GShow, 
-                    Text.GRead.Derive, Text.GRead.Grammar,
-                    Text.GRead.Derive.BindingGroup,
-                    Text.GRead.Transformations.GramTrafo, 
-                    Text.GRead.Transformations.Group, 
-                    Text.GRead.Transformations.LeftCorner,
-                    Text.GRead.Transformations.LeftFact     
-extensions:         Arrows, GADTs, TemplateHaskell
-hs-source-dirs:     src
 extra-source-files: README, LICENSE-LGPL, ChristmasTree.bib
-ghc-options:        -Wall
+
+library
+  exposed-modules:     Text.GRead, Text.GShow, 
+                       Text.GRead.Derive, Text.GRead.Grammar,
+                       Text.GRead.Derive.BindingGroup,
+                       Text.GRead.Transformations.GramTrafo, 
+                       Text.GRead.Transformations.Group, 
+                       Text.GRead.Transformations.LeftCorner,
+                       Text.GRead.Transformations.LeftFact 
+  build-depends:       base >= 4 && < 5, template-haskell >= 2.4, containers,
+                       fgl >= 5.4.2 && < 5.4.3, TTTAS >= 0.4 , uulib >= 0.9.11 
+  extensions:         Arrows, GADTs, TemplateHaskell
+  hs-source-dirs:     src
+
+
+    
+
+
diff --git a/examples/Test.hs b/examples/Test.hs
deleted file mode 100644
--- a/examples/Test.hs
+++ /dev/null
@@ -1,127 +0,0 @@
-module Test where
-
-import Text.GRead
-import Language.AbstractSyntax.TTTAS
-
-infixl 5 :<:, :+:
-infixr 6 :>:, :*:
-
-data T1  =  T1 :<: T1
-         |  T1 :>: T1
-         |  C1
-         deriving (Read, Show)
-
-data T2 a  =  T2 a  :+: T2 a
-           |  a     :*: T2 a
-           |  C2
-         deriving (Read, Show)
-
-data T3 = T3 T4 | C3
-         deriving (Read, Show)
-data T4 = T4 T3 | C4
-         deriving (Read, Show)
-
-
-_0 = Zero
-_1 = Suc _0
-_2 = Suc _1
-
-
-instance Gram T1 where
- grammar = DGrammar _0 envT1
-
-envT1 :: Env DGram ((),T1) ((),T1) 
-envT1 =  consD (nonts _0) Empty 
-     where
-      nonts _T1 = DLNontDefs
-       [  (  DRef (_T1, 5) 
-          ,  DPS  [  dNont (_T1, 5) .#. dTerm ":<:" .#.
-                     dNont (_T1, 6) .#. dEnd infixL ]
-          )
-       ,  (  DRef (_T1, 6) 
-          ,  DPS  [  dNont (_T1, 7) .#. dTerm ":>:" .#.
-                     dNont (_T1, 6) .#. dEnd infixR ] 
-          ) 
-       ,  (  DRef (_T1,10) 
-          ,  DPS  [  dTerm "C1"   .#. dEnd (const C1)
-                  ,  dTerm "(" .#. dNont (_T1,0) .#. 
-                     dTerm ")" .#. dEnd parenT ] 
-          )
-       ]
-      infixL e1 _ e2   = e2 :<: e1
-      infixR e1 _ e2   = e2 :>: e1 
-
-
-instance Gram a => Gram (T2 a) where
- grammar = DGrammar   _0  envT2 
-
-envT2 :: (Gram a) => Env DGram  (((),a),T2 a)
-                                (((),a),T2 a)
-envT2 =  consD (nonts  _0 _1) $ 
-         consG grammar Empty
-     where
-      nonts _T2 _A = DLNontDefs
-       [  (  DRef (_T2, 5) 
-          ,  DPS  [  dNont (_T2,  6)  .#. dTerm ":+:" .#.
-                     dNont (_T2,  6)  .#. dEnd infixP ] 
-          )
-       ,  (  DRef (_T2, 6)
-          ,  DPS  [  dNont (_A,   7)  .#. dTerm ":*:" .#. 
-                     dNont (_T2,  7)  .#. dEnd infixT ] 
-          )
-       ,  (  DRef (_T2,10) 
-          ,  DPS  [  dTerm "C2"   .#. dEnd (const C2)
-                  ,  dTerm "("    .#. dNont (_T2,0) .#. 
-                     dTerm ")"    .#. dEnd parenT ] 
-          )
-       ]
-      infixP   e1 _ e2  = e2 :+: e1
-      infixT   e1 _ e2  = e2 :*: e1 
-
-envT3T4 :: Env DGram (((), T4), T3) (((), T4), T3)
-envT3T4 =  consD (nonts3 _0 _1) $
-           consD (nonts4 _1 _0) Empty  
-     where
-      nonts3 _T3 _T4 = DLNontDefs
-       [  (  DRef (_T3,10) 
-          ,  DPS  [  dTerm "T3" .#. dNont (_T4,0) .#. 
-                     dEnd consT3 
-                  ,  dTerm "C3" .#. dEnd (const C3) 
-                  ,  dTerm "(" .#. dNont (_T3,0) .#. 
-                     dTerm ")" .#. dEnd parenT  
-                  ]
-          )
-       ]
-      nonts4 _T4 _T3 = DLNontDefs
-       [  (  DRef (_T4,10) 
-          ,  DPS  [  dTerm "T4" .#. dNont (_T3,0) .#. 
-                     dEnd consT4 
-                  ,  dTerm "C4" .#. dEnd (const C4) 
-                  ,  dTerm "(" .#. dNont (_T4,0) .#. 
-                     dTerm ")" .#. dEnd parenT  
-                  ]
-          )
-       ]
-      consT3 a  = const (T3 a) 
-      consT4 a  = const (T4 a) 
-
-instance Gram T3 where
- grammar = DGrammar _0 envT3T4
-
-instance Gram T4 where
- grammar = DGrammar _1 envT3T4
-
-read' :: (Gram a) => String -> a
-read' input = case gread input of
-                 Ok  a       -> a
-                 Rep _ (m:_) -> error $ show m
-
-v1 = read' "C1 :>: C1 :>: C1" :: T1
-v2 = read' "C1 :<: C1 :<: C1" :: T1
-v3 = read' "C1 :>: C1 :<: C1 :>: C1" :: T1
-v4 = read' "(((((((((((((C1)))))))))))))" :: T1
-v5 = read' "(C1 :>: C1) :*: C2 :+: C2" :: T2 T1
-v6 = read' "T3 T4 T3 T4 C3" :: T3
-v7 = read' "T4 T3 T4 T3 T4 C3" :: T4
-v8 = read' "bla" :: T1 -- error
-
diff --git a/examples/Test2.hs b/examples/Test2.hs
deleted file mode 100644
--- a/examples/Test2.hs
+++ /dev/null
@@ -1,45 +0,0 @@
-{-# OPTIONS  -XScopedTypeVariables -XRankNTypes #-}
-{-# LANGUAGE TemplateHaskell #-}
-
-module Test2 where
-
-import Text.GRead
-import Text.GRead.Derive
-
-infixl 5 :<:, :+:
-infixr 6 :>:, :*:
-
-data T1  =  T1 :<: T1
-         |  T1 :>: T1
-         |  C1
-         deriving (Read, Show)
-
-data T2 a  =  T2 a  :+: T2 a
-           |  a     :*: T2 a
-           |  C2
-         deriving (Read, Show)
-
-data T3 = T3 T4 | C3
-         deriving (Read, Show)
-data T4 = T4 T3 | C4
-         deriving (Read, Show)
-
-$(deriveGrammar ''T1)
-$(deriveGrammar ''T2)
-$(deriveGrammar ''T3)
-$(deriveGrammar ''T4)
-
-read' :: (Gram a) => String -> a
-read' input = case gread input of
-                 Ok  a       -> a
-                 Rep _ (m:_) -> error $ show m
-
-v1 = read' "C1 :>: C1 :>: C1" :: T1
-v2 = read' "C1 :<: C1 :<: C1" :: T1
-v3 = read' "C1 :>: C1 :<: C1 :>: C1" :: T1
-v4 = read' "(((((((((((((C1)))))))))))))" :: T1
-v5 = read' "(C1 :>: C1) :*: C2 :+: C2" :: T2 T1
-v6 = read' "T3 T4 T3 T4 C3" :: T3
-v7 = read' "T4 T3 T4 T3 T4 C3" :: T4
-v8 = read' "bla" :: T1 -- error
-
diff --git a/examples/TestDerive.hs b/examples/TestDerive.hs
deleted file mode 100644
--- a/examples/TestDerive.hs
+++ /dev/null
@@ -1,128 +0,0 @@
-{-# OPTIONS  -XScopedTypeVariables -XRank2Types #-}
-{-# LANGUAGE TemplateHaskell #-}
-module TestDerive where
-
-import Text.GRead
-import Text.GRead.Derive
-
-
-data T1  =  T1 :<: T1
-         |  T1 :>: T1
-         |  C1
-  deriving Show
-
-data T2 a  =  T2 a  :+: T2 a
-           |  a     :*: T2 a
-           |  C2
-  deriving Show
-
-data T3 = T3 T4 | C3
-  deriving Show
-
-data T4 = T4 T3 | C4
-  deriving Show
-
-data T5 = T5 T6 | C5
-  deriving Show
-
-data T6 = T6 T7
-  deriving Show
-
-data T7 = T7 T5
-  deriving Show
-
-data T8  =  T8 (T2 T8) 
-         |  C8
-  deriving Show
-
-data T9   =  T9 (T2 T10) 
-          |  C9
-  deriving Show
-
-data T10  =  T10 T9
-  deriving Show
-
-data T11  =  T11  (T2 T11) 
-                  (T2 T12) 
-  deriving Show
-
-data T12  =  T12  T11
-  deriving Show
-
-data T13     = T13
-  deriving Show
-
-data T14 a b = T14 a b
-  deriving Show
-
-data T15  =  T15 :-: T1
-          |  C15
-
-data T16  =  T1 :.: T16
-          |  C16
-
-
-$(deriveGrammar ''T1)
-$(deriveGrammar ''T2)
-$(deriveGrammar ''T3)
-$(deriveGrammar ''T4)
-$(deriveGrammar ''T5)
-$(deriveGrammar ''T6)
-$(deriveGrammar ''T7)
-$(deriveGrammar ''T8)
-$(deriveGrammar ''T9)
-$(deriveGrammar ''T10)
-$(deriveGrammar ''T11)
-$(deriveGrammar ''T12)
-
-$(deriveGrammar ''T13)
-
-$(deriveGrammar ''T14)
--- $(deriveGrammar ''T15) -- doesn't work
--- $(deriveGrammar ''T16) -- doesn't work
-
-
-data BT a b c d e 
-  = BT (BT a b c d e) (BT a b c d e) 
-  | O_A a | O_B b | O_C c | O_D d | O_E e  
-  | O_movl | O_movw | O_movb  | O_movzbw | O_movzbl | O_movzwl 
-  | O_movsbw | O_movsbl | O_movswl   | O_pushl | O_popl 
-  | O_pushfl | O_popfl  | O_notl | O_notw | O_notb  | O_sall | O_salw | O_salb
-  | O_sarl | O_sarw | O_sarb  | O_shrl | O_shrw | O_shrb
-  | O_roll | O_rolw | O_rolb  | O_rorl | O_rorw | O_rorb
-  | O_shldl | O_shrdl  | O_addl | O_addw | O_addb
-  | O_adcl  | O_subl | O_subw | O_subb   | O_sbbl
-  | O_imull | O_imulw | O_imulb | O_mull | O_divl | O_divw | O_divb
-  | O_idivl | O_xorl | O_xorw | O_xorb  | O_andl | O_andw | O_andb
-  | O_orl  | O_orw  | O_orb | O_incl | O_incw | O_incb
-  | O_decl | O_decw | O_decb  | O_negl | O_negw | O_negb
-  | O_testl | O_testw | O_testb | O_leal | O_cmpl | O_cmpw | O_cmpb
-  | O_cmpsb | O_scasb | O_movsl | O_movsw | O_movsb
-  | O_stosl | O_stosw | O_stosb | O_leave | O_ret | O_call | O_jmp
-  | O_je | O_jne  | O_jl | O_jle | O_jg | O_jge | O_js | O_jns
-  | O_jz | O_jnz  | O_jc | O_jnc | O_jo | O_jno | O_ja | O_jae
-  | O_jb | O_jbe  | O_jp | O_seta | O_setae | O_setb | O_setbe
-  | O_sete | O_setne | O_setl | O_setle | O_setg | O_setge
-  | O_setc | O_setcb  | O_btl | O_btsl | O_btrl | O_btcl
-  | O_cld  | O_cltd  | O_cwtl  | O_cbtw  | O_rep | O_repz | O_repnz
-  | O_fild | O_fildl | O_fildll  | O_fsubp | O_fsubr | O_fsubrp 
-  | O_fsubrl | O_fsubrs | O_fsubs | O_fsubl | O_fsub
-  | O_faddp | O_fadds | O_faddl | O_fadd | O_fiaddl
-  | O_fmul | O_fmuls | O_fmull | O_fmulp
-  | O_fimull | O_fdiv | O_fdivp | O_fdivr | O_fdivrs | O_fdivrl | O_fdivrp
-  | O_fidivl | O_fidivrl | O_fdivl | O_fdivs
-  | O_fprem  | O_fstp | O_fsts | O_fstps | O_fstl | O_fstpl | O_fstpt | O_fst
-  | O_fistl | O_fistpl | O_fistpll
-  | O_fld | O_flds | O_fldl | O_fldt | O_fldz | O_fld1 | O_fldl2e | O_fldln2
-  | O_fchs  | O_fsin | O_fcos | O_fptan | O_fsqrt | O_fpatan | O_fabs
-  | O_f2xm1 | O_fscale | O_fyl2x
-  | O_fucom | O_fucomp | O_fucompp
-  | O_fcomp | O_fcompp | O_fcoml | O_fcompl | O_ficompl
-  | O_fcoms | O_fcom | O_fcomps  | O_fnstsw | O_fnstcw            
-  | O_fldcw | O_frndint | O_fxch | O_sahf  | O_nop
-    deriving (Show, Eq, Read)
-
-$(deriveGrammar ''BT)
-
-
-res = gread "BT O_nop BT (O_B T10 C9) (O_E T14 C1 C3)" :: GReadResult (BT T1 T10 T11 T12 (T14 T1 T3))
diff --git a/examples/TestShow.hs b/examples/TestShow.hs
deleted file mode 100644
--- a/examples/TestShow.hs
+++ /dev/null
@@ -1,62 +0,0 @@
-{-# OPTIONS -XScopedTypeVariables -XRank2Types #-}
-{-# LANGUAGE TemplateHaskell  #-}
-
-module TestShow where
-
-import Text.GRead
-import Text.GRead.Derive
-
-import Text.GShow
-
-import Language.Haskell.TH
-import Language.Haskell.TH.Syntax
-
-
-data T1 = T1
- deriving Show
-$(deriveShow ''T1)
-
-s1 = gshow T1
-
-data T2 a = T2
-
-$(deriveShow ''T2)
-
-s2 = gshow (T2 :: (T2 T1))
-
-data T3 a = T3 a
-  deriving Show
-
-$(deriveShow ''T3)
-
-s3 = gshow $ T3 T1
-
-infixl 5 :<:
-infixr 6 :>:
-
-data T4 a =  T4 a :<: a
-          |  T4 a :>: T4 a
-          |  C4
- deriving Show
-
-data T5 = T5
- deriving Show
-
-$(deriveShow ''T4)
-$(deriveShow ''T5)
-
-s41 = gshow (C4 :>: C4 :>: C4 :>: C4 :: T4 T5)
-s42 = gshow ((C4 :>: C4) :>: C4 :: T4 T5)
-s43 = gshow (C4 :>: (C4 :>: C4) :: T4 T5)
-s44 = gshow (C4 :>: C4 :>: C4 :<: T5 :: T4 T5)
-s45 = gshow (C4 :>: C4 :>: C4 :<: T5 :<: T5 :: T4 T5)
-
-$(deriveGrammar ''T4)
-$(deriveGrammar ''T5)
-
-v41 = gread s41 :: GReadResult (T4 T5)
-v42 = gread s42 :: GReadResult (T4 T5)
-v43 = gread s43 :: GReadResult (T4 T5)
-v44 = gread s44 :: GReadResult (T4 T5)
-v45 = gread s45 :: GReadResult (T4 T5)
-
diff --git a/src/Text/GRead.hs b/src/Text/GRead.hs
--- a/src/Text/GRead.hs
+++ b/src/Text/GRead.hs
@@ -1,4 +1,6 @@
-{-# OPTIONS  -fglasgow-exts #-}
+{-# LANGUAGE RankNTypes,
+             MagicHash,
+             ScopedTypeVariables #-}
 
 {-| 
     Alternative approach of 'read' that composes grammars instead 
@@ -42,7 +44,7 @@
 import Text.GRead.Transformations.Group
 import UU.Parsing hiding (Symbol,parse,Ok)
 import qualified UU.Parsing as UU
-import List (findIndex)
+import Data.List (findIndex)
 
 
 -- | Type of error repair messages.
diff --git a/src/Text/GRead/Grammar.hs b/src/Text/GRead/Grammar.hs
--- a/src/Text/GRead/Grammar.hs
+++ b/src/Text/GRead/Grammar.hs
@@ -1,5 +1,5 @@
-{-# OPTIONS -fglasgow-exts #-}
-
+{-# LANGUAGE ExistentialQuantification,
+             RankNTypes #-}
 {- | 
 
     Representation of Data Type Grammars.
diff --git a/src/Text/GRead/Transformations/GramTrafo.hs b/src/Text/GRead/Transformations/GramTrafo.hs
--- a/src/Text/GRead/Transformations/GramTrafo.hs
+++ b/src/Text/GRead/Transformations/GramTrafo.hs
@@ -1,4 +1,4 @@
-{-# OPTIONS -fglasgow-exts #-}
+{-# LANGUAGE RankNTypes #-}
 
 module Text.GRead.Transformations.GramTrafo where
 
diff --git a/src/Text/GRead/Transformations/Group.hs b/src/Text/GRead/Transformations/Group.hs
--- a/src/Text/GRead/Transformations/Group.hs
+++ b/src/Text/GRead/Transformations/Group.hs
@@ -1,4 +1,6 @@
-{-# OPTIONS -fglasgow-exts -XArrows #-}
+{-# LANGUAGE Arrows,
+             RankNTypes,
+             ScopedTypeVariables #-}
 
 module Text.GRead.Transformations.Group where
 
@@ -63,8 +65,9 @@
 
 
 group :: DGrammar a -> Grammar a
-group gram 
-    = let trafo =  proc x -> 
+group (gram :: DGrammar a)
+    = let trafo :: forall s t . Trafo Unit Productions s t (Ref a s)
+          trafo =  proc x -> 
                     do (ListDR rs) <- (gGrammar gram) -< x
                        returnA -< plookup 0 rs 
       in  case runTrafo trafo Unit undefined of 
diff --git a/src/Text/GRead/Transformations/LeftCorner.hs b/src/Text/GRead/Transformations/LeftCorner.hs
--- a/src/Text/GRead/Transformations/LeftCorner.hs
+++ b/src/Text/GRead/Transformations/LeftCorner.hs
@@ -1,4 +1,4 @@
-{-# OPTIONS -fglasgow-exts -XArrows #-}
+{-# LANGUAGE Arrows, RankNTypes #-}
 
 module Text.GRead.Transformations.LeftCorner (leftcorner) where
 
diff --git a/src/Text/GRead/Transformations/LeftFact.hs b/src/Text/GRead/Transformations/LeftFact.hs
--- a/src/Text/GRead/Transformations/LeftFact.hs
+++ b/src/Text/GRead/Transformations/LeftFact.hs
@@ -1,4 +1,5 @@
-{-# OPTIONS -fglasgow-exts -XArrows #-}
+{-# LANGUAGE Arrows,
+             ExistentialQuantification #-}
 
 module Text.GRead.Transformations.LeftFact (leftfactoring) where