GHC 6.12.1 has UTF8 support on board. Using System.IO.UTF8 can cause problems.

Therefore use System.IO.UTF8 only on previous versions.
Testet with GHC 6.10.4 and 6.12.1

Commands/Add.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-| 
 
 A history-aware add command to help with data entry.
@@ -6,12 +7,16 @@ A history-aware add command to help with data entry.
 
 module Commands.Add
 where
-import Prelude hiding (putStr, putStrLn, getLine, appendFile)
 import Ledger
 import Options
 import Commands.Register (showRegisterReport)
+#if __GLASGOW_HASKELL__ <= 610
+import Prelude hiding (putStr, putStrLn, getLine, appendFile)
 import System.IO.UTF8
-import System.IO (stderr, hFlush)
+import System.IO ( stderr, hFlush )
+#else
+import System.IO ( stderr, hFlush, hPutStrLn, hPutStr )
+#endif
 import System.IO.Error
 import Text.ParserCombinators.Parsec
 import Utils (ledgerFromStringWithOpts)
@@ -24,9 +29,9 @@ add :: [Opt] -> [String] -> Ledger -> IO ()
 add opts args l
     | filepath (journal l) == "-" = return ()
     | otherwise = do
-  hPutStrLn stderr
-    "Enter one or more transactions, which will be added to your ledger file.\n\
-    \To complete a transaction, enter . as account name. To quit, press control-c."
+  hPutStrLn stderr $
+    "Enter one or more transactions, which will be added to your ledger file.\n"
+    ++"To complete a transaction, enter . as account name. To quit, press control-c."
   today <- getCurrentDay
   getAndAddTransactions l opts args today `catch` (\e -> unless (isEOFError e) $ ioError e)
 

Commands/Balance.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-|
 
 A ledger-compatible @balance@ command.
@@ -96,7 +97,6 @@ balance report:
 
 module Commands.Balance
 where
-import Prelude hiding (putStr)
 import Ledger.Utils
 import Ledger.Types
 import Ledger.Amount
@@ -104,7 +104,10 @@ import Ledger.AccountName
 import Ledger.Posting
 import Ledger.Ledger
 import Options
+#if __GLASGOW_HASKELL__ <= 610
+import Prelude hiding ( putStr )
 import System.IO.UTF8
+#endif
 
 
 -- | Print a balance report.

Commands/Histogram.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-| 
 
 Print a histogram report.
@@ -6,10 +7,12 @@ Print a histogram report.
 
 module Commands.Histogram
 where
-import Prelude hiding (putStr)
 import Ledger
 import Options
+#if __GLASGOW_HASKELL__ <= 610
+import Prelude hiding ( putStr )
 import System.IO.UTF8
+#endif
 
 
 barchar = '*'

Commands/Print.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-| 
 
 A ledger-compatible @print@ command.
@@ -6,10 +7,12 @@ A ledger-compatible @print@ command.
 
 module Commands.Print
 where
-import Prelude hiding (putStr)
 import Ledger
 import Options
+#if __GLASGOW_HASKELL__ <= 610
+import Prelude hiding ( putStr )
 import System.IO.UTF8
+#endif
 
 
 -- | Print ledger transactions in standard format.

Commands/Register.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-| 
 
 A ledger-compatible @register@ command.
@@ -6,10 +7,12 @@ A ledger-compatible @register@ command.
 
 module Commands.Register
 where
-import Prelude hiding (putStr)
 import Ledger
 import Options
+#if __GLASGOW_HASKELL__ <= 610
+import Prelude hiding ( putStr )
 import System.IO.UTF8
+#endif
 
 
 -- | Print a register report.

Commands/Stats.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-|
 
 Print some statistics for the ledger.
@@ -6,10 +7,12 @@ Print some statistics for the ledger.
 
 module Commands.Stats
 where
-import Prelude hiding (putStr)
 import Ledger
 import Options
+#if __GLASGOW_HASKELL__ <= 610
+import Prelude hiding ( putStr )
 import System.IO.UTF8
+#endif
 
 
 -- | Print various statistics for the ledger.

Commands/Web.hs

@@ -6,7 +6,9 @@ A web-based UI.
 
 module Commands.Web
 where
+#if __GLASGOW_HASKELL__ <= 610
 import Codec.Binary.UTF8.String (decodeString)
+#endif
 import Control.Applicative.Error (Failing(Success,Failure))
 import Control.Concurrent
 import Control.Monad.Reader (ask)
@@ -50,7 +52,7 @@ import Commands.Register
 import Ledger
 import Utils (openBrowserOn)
 import Ledger.IO (readLedger)
-
+# 
 -- import Debug.Trace
 -- strace :: Show a => a -> a
 -- strace a = trace (show a) a
@@ -244,8 +246,13 @@ searchform env = do
 addform :: Hack.Env -> HSP XML
 addform env = do
   let inputs = Hack.Contrib.Request.inputs env
+#if __GLASGOW_HASKELL__ <= 610
       date  = decodeString $ fromMaybe "" $ lookup "date"  inputs
       desc  = decodeString $ fromMaybe "" $ lookup "desc"  inputs
+#else
+      date  = fromMaybe "" $ lookup "date"  inputs
+      desc  = fromMaybe "" $ lookup "desc"  inputs
+#endif
   <div>
    <div id="addform">
    <form action="" method="POST">
@@ -268,8 +275,13 @@ addform env = do
 transactionfields :: Int -> Hack.Env -> HSP XML
 transactionfields n env = do
   let inputs = Hack.Contrib.Request.inputs env
+#if __GLASGOW_HASKELL__ <= 610
       acct = decodeString $ fromMaybe "" $ lookup acctvar inputs
       amt  = decodeString $ fromMaybe "" $ lookup amtvar  inputs
+#else
+      acct = fromMaybe "" $ lookup acctvar inputs
+      amt  = fromMaybe "" $ lookup amtvar  inputs
+#endif
   <tr>
     <td>
       [NBSP][NBSP]
@@ -292,12 +304,21 @@ handleAddform l = do
     validate :: Hack.Env -> Day -> Failing Transaction
     validate env today =
         let inputs = Hack.Contrib.Request.inputs env
+#if __GLASGOW_HASKELL__ <= 610
             date  = decodeString $ fromMaybe "today" $ lookup "date"  inputs
             desc  = decodeString $ fromMaybe "" $ lookup "desc"  inputs
             acct1 = decodeString $ fromMaybe "" $ lookup "acct1" inputs
             amt1  = decodeString $ fromMaybe "" $ lookup "amt1"  inputs
             acct2 = decodeString $ fromMaybe "" $ lookup "acct2" inputs
             amt2  = decodeString $ fromMaybe "" $ lookup "amt2"  inputs
+#else
+            date  = fromMaybe "today" $ lookup "date"  inputs
+            desc  = fromMaybe "" $ lookup "desc"  inputs
+            acct1 = fromMaybe "" $ lookup "acct1" inputs
+            amt1  = fromMaybe "" $ lookup "amt1"  inputs
+            acct2 = fromMaybe "" $ lookup "acct2" inputs
+            amt2  = fromMaybe "" $ lookup "amt2"  inputs
+#endif
             validateDate ""  = ["missing date"]
             validateDate _   = []
             validateDesc ""  = ["missing description"]

Ledger/IO.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-|
 Utilities for doing I/O with ledger files.
 -}
@@ -12,8 +13,10 @@ import Ledger.Utils (getCurrentLocalTime)
 import Ledger.Dates (nulldatespan)
 import System.Directory (getHomeDirectory)
 import System.Environment (getEnv)
+#if __GLASGOW_HASKELL__ <= 610
 import Prelude hiding (readFile)
 import System.IO.UTF8
+#endif
 import System.FilePath ((</>))
 import System.Time (getClockTime)
 

Ledger/Parse.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-|
 
 Parsers for standard ledger and timelog files.
@@ -6,13 +7,15 @@ Parsers for standard ledger and timelog files.
 
 module Ledger.Parse
 where
-import Prelude hiding (readFile, putStr, putStrLn, print, getContents)
 import Control.Monad.Error (ErrorT(..), MonadIO, liftIO, throwError, catchError)
 import Text.ParserCombinators.Parsec
 import Text.ParserCombinators.Parsec.Char
 import Text.ParserCombinators.Parsec.Combinator
 import System.Directory
+#if __GLASGOW_HASKELL__ <= 610
+import Prelude hiding (readFile, putStr, putStrLn, print, getContents)
 import System.IO.UTF8
+#endif
 import Ledger.Utils
 import Ledger.Types
 import Ledger.Dates

Ledger/Utils.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-|
 
 Provide standard imports and utilities which are useful everywhere, or
@@ -23,7 +24,6 @@ module Text.RegexPR,
 module Test.HUnit,
 )
 where
-import Prelude hiding (readFile)
 import Char
 import Control.Exception
 import Control.Monad
@@ -36,7 +36,10 @@ import Data.Time.Clock
 import Data.Time.Calendar
 import Data.Time.LocalTime
 import Debug.Trace
+#if __GLASGOW_HASKELL__ <= 610
+import Prelude hiding (readFile)
 import System.IO.UTF8
+#endif
 import Test.HUnit
 import Text.Printf
 import Text.RegexPR

Options.hs

@@ -11,7 +11,9 @@ import Ledger.IO (myLedgerPath,myTimelogPath)
 import Ledger.Utils
 import Ledger.Types
 import Ledger.Dates
+#if __GLASGOW_HASKELL__ <= 610
 import Codec.Binary.UTF8.String (decodeString)
+#endif
 import Control.Monad (liftM)
 
 progname      = "hledger"
@@ -149,7 +151,11 @@ optValuesForConstructors fs opts = concatMap get opts
 -- YYYY/MM/DD format based on the current time.
 parseArguments :: IO ([Opt], String, [String])
 parseArguments = do
+#if __GLASGOW_HASKELL__ <= 610
   args <- liftM (map decodeString) getArgs
+#else
+  args <- getArgs
+#endif
   let (os,as,es) = getOpt Permute options args
 --  istimequery <- usingTimeProgramName
 --  let os' = if istimequery then (Period "today"):os else os

Utils.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-|
 
 Utilities for top-level modules and ghci. See also "Ledger.IO" and
@@ -12,7 +13,11 @@ import Ledger
 import Options (Opt(..),ledgerFilePathFromOpts) -- ,optsToFilterSpec)
 import System.Directory (doesFileExist)
 import System.IO (stderr)
+#if __GLASGOW_HASKELL__ <= 610
 import System.IO.UTF8 (hPutStrLn)
+#else
+import System.IO (hPutStrLn)
+#endif
 import System.Exit
 import System.Cmd (system)
 import System.Info (os)

hledger.hs

@@ -36,8 +36,10 @@ See "Ledger.Ledger" for more examples.
 -}
 
 module Main where
+#if __GLASGOW_HASKELL__ <= 610
 import Prelude hiding (putStr, putStrLn)
 import System.IO.UTF8
+#endif
 
 import Commands.All
 import Ledger