diff --git a/cbits/chsmpfr.c b/cbits/chsmpfr.c
--- a/cbits/chsmpfr.c
+++ b/cbits/chsmpfr.c
@@ -120,6 +120,22 @@
 void mpfr_custom_move_wrap (mpfr_ptr p1, void *p2 ) {
   mpfr_custom_move(p1, p2);
 }
+
+int mpfr_const_pi_wrap (mpfr_ptr p1, int p2) {
+  return mpfr_const_pi(p1,p2);
+}
+
+int mpfr_const_log2_wrap (mpfr_ptr p1, int p2) {
+  return mpfr_const_log2(p1,p2);
+}
+
+int mpfr_const_euler_wrap (mpfr_ptr p1, int p2) {
+  return mpfr_const_euler(p1,p2);
+}
+int mpfr_const_catalan_wrap (mpfr_ptr p1, int p2) {
+  return mpfr_const_catalan(p1,p2);
+}
+
 /*
 intmax_t mpfr_get_sj_wrap (mpfr_ptr p1, mp_rnd_t p2) {
   return mpfr_get_sj(p1, p2);
diff --git a/cbits/chsmpfr.h b/cbits/chsmpfr.h
--- a/cbits/chsmpfr.h
+++ b/cbits/chsmpfr.h
@@ -71,3 +71,12 @@
 mp_exp_t mpfr_custom_get_exp_wrap(const mpfr_ptr ) ;
 
 void mpfr_custom_move_wrap (const mpfr_ptr , void * ) ;
+
+int mpfr_const_pi_wrap (const mpfr_ptr , int );
+
+
+int mpfr_const_log2_wrap (const mpfr_ptr , int );
+
+int mpfr_const_euler_wrap (const mpfr_ptr , int );
+
+int mpfr_const_catalan__wrap (const mpfr_ptr , int );
diff --git a/hmpfr.cabal b/hmpfr.cabal
--- a/hmpfr.cabal
+++ b/hmpfr.cabal
@@ -1,5 +1,5 @@
 name:                hmpfr
-version:             0.3
+version:             0.3.1
 synopsis:            Haskell binding to MPFR library
 description:         Haskell binding to MPFR library. This version is compatible
                      only with 2.4.* and will not work with previous releases
@@ -30,8 +30,10 @@
 
 Library
   build-Depends:       base > 3 && < 5
-  if impl(ghc >= 6.10)
+  if impl(ghc >= 6.10) && impl(ghc < 6.12)
      build-Depends:    base >= 4, integer
+  if impl(ghc >= 6.12)
+     build-Depends:    integer-gmp
 
   Other-modules:       Data.Number.MPFR.FFIhelper
                        Data.Number.MPFR.Internal
diff --git a/src/Data/Number/MPFR/Conversion.hs b/src/Data/Number/MPFR/Conversion.hs
--- a/src/Data/Number/MPFR/Conversion.hs
+++ b/src/Data/Number/MPFR/Conversion.hs
@@ -102,15 +102,14 @@
                                   else '.' : bt
                            else head ss : '.' :
                                 let bt = (backtrim . tail) ss 
-                                in if null bt 
-                                   then "0"
-                                   else bt ++ "e" ++ show (pred e)
+                                in (if null bt then "0" else bt) 
+                                   ++ "e" ++ show (pred e)
                   | otherwise = 
-                      head ss : '.' : 
+                      s ++ (head ss : '.' : 
                                (let bt = (backtrim . tail) ss in
                                 if null bt then "0" 
                                 else bt )
-                               ++ "e" ++ show (pred e)
+                               ++ "e" ++ show (pred e))
                     where (str, e') = mpfrToString Near n 10 d
                           e = fromIntegral e'
                           n        = max dec 5
diff --git a/src/Data/Number/MPFR/FFIhelper.hsc b/src/Data/Number/MPFR/FFIhelper.hsc
--- a/src/Data/Number/MPFR/FFIhelper.hsc
+++ b/src/Data/Number/MPFR/FFIhelper.hsc
@@ -571,16 +571,16 @@
         mpfr_hypot :: Ptr MPFR -> Ptr MPFR -> Ptr MPFR -> CRoundMode -> IO CInt  
 
 -- constants
-foreign import ccall unsafe "mpfr_const_log2"
+foreign import ccall unsafe "mpfr_const_log2_wrap"
         mpfr_const_log2 :: Ptr MPFR -> CRoundMode -> IO CInt
 
-foreign import ccall unsafe "mpfr_const_pi"
+foreign import ccall unsafe "mpfr_const_pi_wrap"
         mpfr_const_pi :: Ptr MPFR -> CRoundMode -> IO CInt
 
-foreign import ccall unsafe "mpfr_const_euler"
+foreign import ccall unsafe "mpfr_const_euler_wrap"
         mpfr_const_euler :: Ptr MPFR -> CRoundMode -> IO CInt
 
-foreign import ccall unsafe "mpfr_const_catalan"
+foreign import ccall unsafe "mpfr_const_catalan_wrap"
         mpfr_const_catalan :: Ptr MPFR -> CRoundMode -> IO CInt
 
 foreign import ccall unsafe "mpfr_free_cache"
diff --git a/src/Data/Number/MPFR/Instances/Down.hs b/src/Data/Number/MPFR/Instances/Down.hs
--- a/src/Data/Number/MPFR/Instances/Down.hs
+++ b/src/Data/Number/MPFR/Instances/Down.hs
@@ -34,13 +34,14 @@
 
 import Data.Ratio
 
-#if __GLASGOW_HASKELL__ >= 610
+
+#if (__GLASGOW_HASKELL__ >= 610) && (__GLASGOW_HASKELL__ < 612)
 import GHC.Integer.Internals
-import GHC.Exts hiding (Down)
-#else 
-import GHC.Exts
+#elif __GLASGOW_HASKELL__ >= 612
+import GHC.Integer.GMP.Internals
 #endif
 
+import qualified GHC.Exts as E
 
 instance Num MPFR where
     d + d'        = A.add Down (maxPrec d d') d d'
@@ -49,8 +50,8 @@
     negate d      = A.neg Down (getPrec d) d
     abs d         = A.absD Down (getPrec d) d
     signum        = fromInt Down minPrec . fromMaybe (-1) .sgn
-    fromInteger (S# i) = fromInt Down minPrec (I# i)
-    fromInteger i@(J# n _) = fromIntegerA Zero (fromIntegral . abs $ I# n * bitsPerIntegerLimb) i 
+    fromInteger (S# i) = fromInt Down minPrec (E.I# i)
+    fromInteger i@(J# n _) = fromIntegerA Zero (fromIntegral . abs $ E.I# n * bitsPerIntegerLimb) i 
 
 instance Real MPFR where
     toRational d = n % 2 ^ e
diff --git a/src/Data/Number/MPFR/Instances/Near.hs b/src/Data/Number/MPFR/Instances/Near.hs
--- a/src/Data/Number/MPFR/Instances/Near.hs
+++ b/src/Data/Number/MPFR/Instances/Near.hs
@@ -34,11 +34,14 @@
 
 import Data.Ratio
 
-#if __GLASGOW_HASKELL__ >= 610
+#if (__GLASGOW_HASKELL__ >= 610) && (__GLASGOW_HASKELL__ < 612)
 import GHC.Integer.Internals
+#elif __GLASGOW_HASKELL__ >= 612
+import GHC.Integer.GMP.Internals
 #endif
-import GHC.Exts
 
+import qualified GHC.Exts as E
+
 instance Num MPFR where
     d + d'        = A.add Near (maxPrec d d') d d'
     d - d'        = A.sub Near (maxPrec d d') d d'
@@ -46,8 +49,8 @@
     negate d      = A.neg Near (getPrec d) d
     abs d         = A.absD Near (getPrec d) d
     signum        = fromInt Near minPrec . fromMaybe (-1) . sgn
-    fromInteger (S# i) = fromInt Near minPrec (I# i)
-    fromInteger i@(J# n _) = fromIntegerA Zero (fromIntegral . abs $ I# n * bitsPerIntegerLimb) i 
+    fromInteger (S# i) = fromInt Near minPrec (E.I# i)
+    fromInteger i@(J# n _) = fromIntegerA Zero (fromIntegral . abs $ E.I# n * bitsPerIntegerLimb) i 
 
 instance Real MPFR where
     toRational d = n % 2 ^ e
diff --git a/src/Data/Number/MPFR/Instances/Up.hs b/src/Data/Number/MPFR/Instances/Up.hs
--- a/src/Data/Number/MPFR/Instances/Up.hs
+++ b/src/Data/Number/MPFR/Instances/Up.hs
@@ -35,11 +35,14 @@
 
 import Data.Ratio
 
-#if __GLASGOW_HASKELL__ >= 610
+#if (__GLASGOW_HASKELL__ >= 610) && (__GLASGOW_HASKELL__ < 612)
 import GHC.Integer.Internals
+#elif __GLASGOW_HASKELL__ >= 612
+import GHC.Integer.GMP.Internals
 #endif
-import GHC.Exts
 
+import qualified GHC.Exts as E
+
 instance Num MPFR where
     d + d'        = A.add Up (maxPrec d d') d d'
     d - d'        = A.sub Up (maxPrec d d') d d'
@@ -47,8 +50,8 @@
     negate d      = A.neg Up (getPrec d) d
     abs d         = A.absD Up (getPrec d) d
     signum        = fromInt Up minPrec . fromMaybe (-1) . sgn
-    fromInteger (S# i) = fromInt Up minPrec (I# i)
-    fromInteger i@(J# n _) = fromIntegerA Zero (fromIntegral . abs $ I# n * bitsPerIntegerLimb) i 
+    fromInteger (S# i) = fromInt Up minPrec (E.I# i)
+    fromInteger i@(J# n _) = fromIntegerA Zero (fromIntegral . abs $ E.I# n * bitsPerIntegerLimb) i 
 
 instance Real MPFR where
     toRational d = n % 2 ^ e
diff --git a/src/Data/Number/MPFR/Instances/Zero.hs b/src/Data/Number/MPFR/Instances/Zero.hs
--- a/src/Data/Number/MPFR/Instances/Zero.hs
+++ b/src/Data/Number/MPFR/Instances/Zero.hs
@@ -34,11 +34,14 @@
 
 import Data.Ratio
 
-#if __GLASGOW_HASKELL__ >= 610
+#if (__GLASGOW_HASKELL__ >= 610) && (__GLASGOW_HASKELL__ < 612)
 import GHC.Integer.Internals
+#elif __GLASGOW_HASKELL__ >= 612
+import GHC.Integer.GMP.Internals
 #endif
-import GHC.Exts
 
+import qualified GHC.Exts as E
+
 instance Num MPFR where
     d + d'        = A.add Zero (maxPrec d d') d d'
     d - d'        = A.sub Zero (maxPrec d d') d d'
@@ -46,8 +49,8 @@
     negate d      = A.neg Zero (getPrec d) d
     abs d         = A.absD Zero (getPrec d) d
     signum        = fromInt Zero minPrec . fromMaybe (-1) . sgn
-    fromInteger (S# i) = fromInt Zero minPrec (I# i)
-    fromInteger i@(J# n _) = fromIntegerA Zero (fromIntegral . abs $ I# n * bitsPerIntegerLimb) i 
+    fromInteger (S# i) = fromInt Zero minPrec (E.I# i)
+    fromInteger i@(J# n _) = fromIntegerA Zero (fromIntegral . abs $ E.I# n * bitsPerIntegerLimb) i 
 
 instance Real MPFR where
     toRational d = n % 2 ^ e
diff --git a/src/Data/Number/MPFR/Special.hs b/src/Data/Number/MPFR/Special.hs
--- a/src/Data/Number/MPFR/Special.hs
+++ b/src/Data/Number/MPFR/Special.hs
@@ -180,13 +180,13 @@
 pi r = fst . pi_ r
 
 log2c   :: RoundMode -> Precision -> MPFR
-log2c r = fst . pi_ r
+log2c r = fst . log2c_ r
 
 euler   :: RoundMode -> Precision -> MPFR
-euler r = fst . pi_ r
+euler r = fst . euler_ r
 
 catalan   :: RoundMode -> Precision -> MPFR
-catalan r = fst . pi_ r
+catalan r = fst . catalan_ r
 
 
 log_       :: RoundMode -> Precision -> MPFR -> (MPFR, Int)