diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -2,6 +2,12 @@
 
 ## Unreleased changes
 
+## 0.1.1.0
+
+* re-export `Default` class from `Numeric.Optimization.MIP`.
+* fix to work with recent version of CBC
+* generalize type of `parseLPString` and `parseMPSString`
+
 ## 0.1.0.0
 
 * Separated from toysolver package
diff --git a/MIP.cabal b/MIP.cabal
--- a/MIP.cabal
+++ b/MIP.cabal
@@ -4,10 +4,10 @@
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: ac803e98baaa0544b947d71e759475b741c54bd5c39105056cfd3d1fbc25b4e0
+-- hash: f6b1b8d7874f11e9e522f0bba9ad5789dbfe74e4a863836348e4a8f03c658484
 
 name:           MIP
-version:        0.1.0.0
+version:        0.1.1.0
 synopsis:       Library for using Mixed Integer Programming (MIP)
 description:    Please see the README on GitHub at <https://github.com/msakai/haskell-MIP/tree/master/MIP#readme>
 category:       Math, Algorithms, Optimisation, Optimization
@@ -31,32 +31,32 @@
   location: https://github.com/msakai/haskell-MIP
 
 flag TestCBC
-  description: run test cases that depends on cbc command
+  description: run test cases that depend on cbc command
   manual: True
   default: False
 
 flag TestCPLEX
-  description: run test cases that depends on cplex command
+  description: run test cases that depend on cplex command
   manual: True
   default: False
 
 flag TestGlpsol
-  description: run test cases that depends on glpsol command
+  description: run test cases that depend on glpsol command
   manual: True
   default: False
 
 flag TestGurobiCl
-  description: run test cases that depends on gurobi_cl command
+  description: run test cases that depend on gurobi_cl command
   manual: True
   default: False
 
 flag TestLPSolve
-  description: run test cases that depends on lp_solve command
+  description: run test cases that depend on lp_solve command
   manual: True
   default: False
 
 flag TestSCIP
-  description: run test cases that depends on scip command
+  description: run test cases that depend on scip command
   manual: True
   default: False
 
@@ -101,7 +101,7 @@
     , filepath
     , intern >=0.9.1.2 && <1.0.0.0
     , lattices
-    , megaparsec >=5 && <9
+    , megaparsec >=5 && <10
     , mtl >=2.1.2
     , process >=1.1.0.2
     , scientific
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -1,5 +1,9 @@
 # MIP
 
+[![Hackage](https://img.shields.io/hackage/v/MIP.svg)](https://hackage.haskell.org/package/MIP)
+[![Hackage Deps](https://img.shields.io/hackage-deps/v/MIP.svg)](https://packdeps.haskellers.com/feed?needle=MIP)
+[![License](https://img.shields.io/badge/License-BSD%203--Clause-blue.svg)](https://opensource.org/licenses/BSD-3-Clause)
+
 Library for using Mixed Integer Programming (MIP) in Haskell.
 This library contains functions like:
 
diff --git a/src/Numeric/Optimization/MIP.hs b/src/Numeric/Optimization/MIP.hs
--- a/src/Numeric/Optimization/MIP.hs
+++ b/src/Numeric/Optimization/MIP.hs
@@ -1,7 +1,9 @@
 {-# OPTIONS_GHC -Wall #-}
 {-# OPTIONS_HADDOCK show-extensions #-}
 {-# LANGUAGE CPP #-}
+{-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE TypeFamilies #-}
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Numeric.Optimization.MIP
@@ -16,28 +18,39 @@
 --
 -----------------------------------------------------------------------------
 module Numeric.Optimization.MIP
-  ( module Numeric.Optimization.MIP.Base
+  (
+  -- * The MIP Problem/Solution types
+    module Numeric.Optimization.MIP.Base
+
+  -- * File I/O
+  -- $IO
+
+  -- ** Reading problem files
   , readFile
   , readLPFile
   , readMPSFile
   , parseLPString
   , parseMPSString
+  , ParseError
+
+  -- ** Generating problem files
   , writeFile
   , writeLPFile
   , writeMPSFile
   , toLPString
   , toMPSString
-  , ParseError
   ) where
 
 import Prelude hiding (readFile, writeFile)
 import Control.Exception
 import Data.Char
 import Data.Scientific (Scientific)
+import Data.String
 import qualified Data.Text.Lazy as TL
 import qualified Data.Text.Lazy.IO as TLIO
 import System.FilePath (takeExtension, splitExtension)
 import System.IO hiding (readFile, writeFile)
+import Text.Megaparsec (Stream (..))
 
 import Numeric.Optimization.MIP.Base
 import Numeric.Optimization.MIP.FileUtils (ParseError)
@@ -52,7 +65,7 @@
 import GHC.IO.Encoding (getLocaleEncoding)
 #endif
 
--- | Parse .lp or .mps file based on file extension
+-- | Parse LP or MPS file based on file extension.
 readFile :: FileOptions -> FilePath -> IO (Problem Scientific)
 readFile opt fname =
   case getExt fname of
@@ -105,13 +118,22 @@
 #endif
 
 -- | Parse a string containing LP file data.
-parseLPString :: FileOptions -> String -> String -> Either (ParseError String) (Problem Scientific)
+#if MIN_VERSION_megaparsec(6,0,0)
+parseLPString :: (Stream s, Token s ~ Char, IsString (Tokens s)) => FileOptions -> String -> s -> Either (ParseError s) (Problem Scientific)
+#else
+parseLPString :: (Stream s, Token s ~ Char) => FileOptions -> String -> s -> Either (ParseError s) (Problem Scientific)
+#endif
 parseLPString = LPFile.parseString
 
 -- | Parse a string containing MPS file data.
-parseMPSString :: FileOptions -> String -> String -> Either (ParseError String) (Problem Scientific)
+#if MIN_VERSION_megaparsec(6,0,0)
+parseMPSString :: (Stream s, Token s ~ Char, IsString (Tokens s)) => FileOptions -> String -> s -> Either (ParseError s) (Problem Scientific)
+#else
+parseMPSString :: (Stream s, Token s ~ Char) => FileOptions -> String -> s -> Either (ParseError s) (Problem Scientific)
+#endif
 parseMPSString = MPSFile.parseString
 
+-- | Generate LP file or MPS file based on file extension.
 writeFile :: FileOptions -> FilePath -> Problem Scientific -> IO ()
 writeFile opt fname prob =
   case getExt fname of
@@ -127,12 +149,14 @@
 #endif
     s -> s
 
+-- | Generate LP file.
 writeLPFile :: FileOptions -> FilePath -> Problem Scientific -> IO ()
 writeLPFile opt fname prob =
   case LPFile.render opt prob of
     Left err -> ioError $ userError err
     Right s -> writeTextFile opt fname s
 
+-- | Generate MPS file.
 writeMPSFile :: FileOptions -> FilePath -> Problem Scientific -> IO ()
 writeMPSFile opt fname prob =
   case MPSFile.render opt prob of
@@ -159,8 +183,14 @@
   writeSimple
 #endif
 
+-- | Generate a 'TL.Text' containing LP file data.
 toLPString :: FileOptions -> Problem Scientific -> Either String TL.Text
 toLPString = LPFile.render
 
+-- | Generate a 'TL.Text' containing MPS file data.
 toMPSString :: FileOptions -> Problem Scientific -> Either String TL.Text
 toMPSString = MPSFile.render
+
+-- $IO
+-- If this library is built with @WithZlib@ flag (enabled by default), 
+-- reading/writing gzipped file (@.gz@) are also supported.
diff --git a/src/Numeric/Optimization/MIP/Base.hs b/src/Numeric/Optimization/MIP/Base.hs
--- a/src/Numeric/Optimization/MIP/Base.hs
+++ b/src/Numeric/Optimization/MIP/Base.hs
@@ -77,6 +77,7 @@
   , FileOptions (..)
 
   -- * Utilities
+  , Default (..)
   , Variables (..)
   , intersectBounds
   ) where
@@ -269,16 +270,19 @@
   }
   deriving (Eq, Ord, Show)
 
+-- | Equality constraint.
 (.==.) :: Num c => Expr c -> Expr c -> Constraint c
 lhs .==. rhs =
   case splitConst (lhs - rhs) of
     (e, c) -> def{ constrExpr = e, constrLB = Finite (- c), constrUB = Finite (- c) }
 
+-- | Inequality constraint (≤).
 (.<=.) :: Num c => Expr c -> Expr c -> Constraint c
 lhs .<=. rhs =
   case splitConst (lhs - rhs) of
     (e, c) -> def{ constrExpr = e, constrUB = Finite (- c) }
 
+-- | Inequality constraint (≥).
 (.>=.) :: Num c => Expr c -> Expr c -> Constraint c
 lhs .>=. rhs =
   case splitConst (lhs - rhs) of
@@ -356,7 +360,9 @@
         , (StatusInfeasibleOrUnbounded, StatusInfeasible)
         ]
 
-
+-- | /meet/ (greatest lower bound) operator of the partial order of 'Status' type.
+--
+-- If the version of @lattices@ is \<2, then @MeetSemiLattice@ instance can also be used.
 meetStatus :: Status -> Status -> Status
 StatusUnknown `meetStatus` _b = StatusUnknown
 StatusFeasible `meetStatus` b
@@ -387,6 +393,7 @@
 #endif
 
 
+-- | Type for representing a solution of MIP problem.
 data Solution r
   = Solution
   { solStatus :: Status
diff --git a/src/Numeric/Optimization/MIP/FileUtils.hs b/src/Numeric/Optimization/MIP/FileUtils.hs
--- a/src/Numeric/Optimization/MIP/FileUtils.hs
+++ b/src/Numeric/Optimization/MIP/FileUtils.hs
@@ -21,6 +21,9 @@
 #endif
 import qualified Text.Megaparsec as MP
 
+-- | Error type for parsing.
+--
+-- The definition is slightly different based on the @megaparsec@ version.
 #if MIN_VERSION_megaparsec(7,0,0)
 type ParseError s = MP.ParseErrorBundle s Void
 #elif MIN_VERSION_megaparsec(6,0,0)
diff --git a/src/Numeric/Optimization/MIP/LPFile.hs b/src/Numeric/Optimization/MIP/LPFile.hs
--- a/src/Numeric/Optimization/MIP/LPFile.hs
+++ b/src/Numeric/Optimization/MIP/LPFile.hs
@@ -17,7 +17,7 @@
 -- Stability   :  provisional
 -- Portability :  non-portable
 --
--- A CPLEX .lp format parser library.
+-- A CPLEX @.lp@ format parser library.
 --
 -- References:
 --
@@ -87,7 +87,7 @@
 #endif
 
 -- | Parse a string containing LP file data.
--- The source name is only | used in error messages and may be the empty string.
+-- The source name is only used in error messages and may be the empty string.
 #if MIN_VERSION_megaparsec(6,0,0)
 parseString :: (Stream s, Token s ~ Char, IsString (Tokens s)) => MIP.FileOptions -> String -> s -> Either (ParseError s) (MIP.Problem Scientific)
 #else
@@ -484,7 +484,7 @@
 
 -- ---------------------------------------------------------------------------
 
--- | Render a problem into a string.
+-- | Render a problem into a 'TL.Text' containing LP file data.
 render :: MIP.FileOptions -> MIP.Problem Scientific -> Either String TL.Text
 render _ mip = Right $ execM $ render' $ normalize mip
 
diff --git a/src/Numeric/Optimization/MIP/MPSFile.hs b/src/Numeric/Optimization/MIP/MPSFile.hs
--- a/src/Numeric/Optimization/MIP/MPSFile.hs
+++ b/src/Numeric/Optimization/MIP/MPSFile.hs
@@ -16,7 +16,7 @@
 -- Stability   :  provisional
 -- Portability :  non-portable
 --
--- A .mps format parser library.
+-- A @.mps@ format parser library.
 --
 -- References:
 --
@@ -104,7 +104,7 @@
 #endif
 
 -- | Parse a string containing MPS file data.
--- The source name is only | used in error messages and may be the empty string.
+-- The source name is only used in error messages and may be the empty string.
 #if MIN_VERSION_megaparsec(6,0,0)
 parseString :: (Stream s, Token s ~ Char, IsString (Tokens s)) => MIP.FileOptions -> String -> s -> Either (ParseError s) (MIP.Problem Scientific)
 #else
@@ -617,6 +617,7 @@
 
 -- ---------------------------------------------------------------------------
 
+-- | Render a problem into a 'TL.Text' containing MPS file data.
 render :: MIP.FileOptions -> MIP.Problem Scientific -> Either String TL.Text
 render _ mip | not (checkAtMostQuadratic mip) = Left "Expression must be atmost quadratic"
 render _ mip = Right $ execM $ render' $ nameRows mip
diff --git a/src/Numeric/Optimization/MIP/Solver/CBC.hs b/src/Numeric/Optimization/MIP/Solver/CBC.hs
--- a/src/Numeric/Optimization/MIP/Solver/CBC.hs
+++ b/src/Numeric/Optimization/MIP/Solver/CBC.hs
@@ -41,7 +41,7 @@
 
 instance IsSolver CBC IO where
   solve solver opt prob = do
-    case LPFile.render def prob of
+    case LPFile.render def prob{ MIP.objectiveFunction = obj' } of
       Left err -> ioError $ userError err
       Right lp -> do
         withSystemTempFile "cbc.lp" $ \fname1 h1 -> do
@@ -61,7 +61,11 @@
               ExitFailure n -> ioError $ userError $ "exit with " ++ show n
               ExitSuccess -> do
                 sol <- CBCSol.readFile fname2
-                if MIP.objDir (MIP.objectiveFunction prob) == MIP.OptMax then
+                if isMax then
                   return $ sol{ MIP.solObjectiveValue = fmap negate (MIP.solObjectiveValue sol) }
                 else
                   return sol
+    where
+      obj = MIP.objectiveFunction prob
+      isMax = MIP.objDir obj == MIP.OptMax
+      obj' = if isMax then obj{ MIP.objDir = MIP.OptMin, MIP.objExpr = - MIP.objExpr obj } else obj
diff --git a/test/TestSuite.hs b/test/TestSuite.hs
--- a/test/TestSuite.hs
+++ b/test/TestSuite.hs
@@ -8,7 +8,7 @@
 import Test.MPSFile
 
 main :: IO ()
-main = defaultMain $ testGroup "ToySolver test suite"
+main = defaultMain $ testGroup "MIP test suite"
   [ lpTestGroup
   , mipTestGroup
   , mipSolverTestGroup