diff --git a/LICENSE b/LICENSE
new file mode 100644
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,30 @@
+Copyright (c) 2013, Liyang HU
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+
+    * Neither the name of Liyang HU nor the names of other
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/Setup.hs b/Setup.hs
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--- /dev/null
+++ b/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/assert.cabal b/assert.cabal
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--- /dev/null
+++ b/assert.cabal
@@ -0,0 +1,45 @@
+name:           assert
+version:        0.0.1.0
+synopsis:       Helpers for Control.Exception.assert
+description:
+    GHC supports compile-time toggling of run-time assertions via the
+    @-fignore-asserts@ flag, which only effects a behavioural change in
+    'Control.Exception.assert'. Furthermore the reported location only gives
+    the use site of the aforementioned, making it difficult to abstract over
+    and hence cumbersome to use.
+    .
+    This package aims to make assertions more convenient, and also provides
+    a rule to rewrite assertions to 'id' when @-fignore-asserts@ is used.
+homepage:       https://github.com/liyang/assert
+license:        BSD3
+license-file:   LICENSE
+author:         Liyang HU
+maintainer:     assert@liyang.hu
+copyright:      © 2013 Liyang HU
+category:       Control
+build-type:     Simple
+cabal-version:  >= 1.8
+stability:      experimental
+
+source-repository head
+    type:       git
+    location:   http://github.com/liyang/assert
+
+library
+    hs-source-dirs: src
+    exposed-modules:
+        Control.Exception.Assert
+    build-depends:
+        base >= 4 && <= 9000
+    ghc-options: -Wall
+
+test-suite rewrite
+    type: exitcode-stdio-1.0
+    hs-source-dirs: tests
+    main-is: rewrite.hs
+    build-depends: assert, base, Cabal, directory, filepath,
+        system-posix-redirect >= 1.0.0.1
+    ghc-options: -Wall -fignore-asserts
+
+-- vim: et sw=4 ts=4 sts=4:
+
diff --git a/src/Control/Exception/Assert.hs b/src/Control/Exception/Assert.hs
new file mode 100644
--- /dev/null
+++ b/src/Control/Exception/Assert.hs
@@ -0,0 +1,72 @@
+{-# LANGUAGE DeriveDataTypeable #-}
+{-# OPTIONS_GHC -fno-warn-orphans #-}
+
+module Control.Exception.Assert
+    ( module Control.Exception.Assert
+    , assert
+    ) where
+
+import Prelude
+import Control.Applicative
+import Control.Exception
+import Data.Data
+
+-- | A distict 'Exception' from 'AssertionFailed', so that we stop fudging
+-- the exception message after the first 'mapException'.
+--
+-- The name comes from abbreviating ‘assert’ and translating the result to
+-- my native tongue.
+newtype Arse = Arse String deriving (Typeable)
+instance Show Arse where show (Arse s) = s
+instance Exception Arse where
+    fromException se = do
+        AssertionFailed failure <- fromException se
+        return (Arse failure)
+
+-- | Generic helper for 'assert' that includes a descriptive message to the
+-- 'AssertFailure' exception if thrown. Use this to build your own 'assert'
+-- helpers, such as 'byOrd'. A rule is included which rewrites
+-- 'assertMessage' to 'id' when compiling with @-fignore-asserts@.
+{-# INLINE [1] assertMessage #-}
+{-# RULES "assertMessage" forall name msg.
+    assertMessage name msg (\x -> x) = id #-}
+assertMessage :: String -> String -> (a -> a) -> a -> a
+assertMessage name msg arse = mapException describe . arse where
+    describe (AssertionFailed failure) = Arse $
+        oneline failure ++ " \"" ++ name ++ "\", " ++ msg
+    oneline = filter ((&&) <$> (/=) '\n' <*> (/=) '\r')
+
+-- | Assert that two values are equal.
+--
+-- >>> byEq assert "Bool" False True ()
+-- *** Exception: … Assertion failed "Bool", False ≠ True
+{-# INLINE byEq #-}
+byEq :: (Eq x, Show x) => (Bool -> a -> a) -> String ->
+    x -> x -> a -> a
+byEq arse name x y = assertMessage name
+    (show x ++ " ≠ " ++ show y) (arse $ x == y)
+
+-- | Assert that two values obey the given 'Ordering'.
+--
+-- >>> byOrd assert "Int" LT 0 1 ()
+-- ()
+{-# INLINE byOrd #-}
+byOrd :: (Ord x, Show x) => (Bool -> a -> a) -> String ->
+    Ordering -> x -> x -> a -> a
+byOrd arse name o x y = assertMessage name
+    (show x ++ no ++ show y) (arse $ o == compare x y)
+  where
+    no = case o of
+        LT -> " ≮ "
+        EQ -> " ≠ "
+        GT -> " ≯ "
+
+-- | Assert that a value satisfies the given predicate.
+--
+-- >>> byPred assert "Odd" odd 4 ()
+-- *** Exception: … Assertion failed "Odd", 4
+{-# INLINE byPred #-}
+byPred :: (Show x) => (Bool -> a -> a) -> String ->
+    (x -> Bool) -> x -> a -> a
+byPred arse name p x = assertMessage name (show x) (arse $ p x)
+
diff --git a/tests/rewrite.hs b/tests/rewrite.hs
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--- /dev/null
+++ b/tests/rewrite.hs
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+import Prelude
+import Control.Exception.Assert
+import Control.Monad
+import Distribution.PackageDescription
+import Distribution.Simple
+import Distribution.Simple.LocalBuildInfo
+import Distribution.Simple.Setup
+import System.Directory
+import System.Exit
+import System.FilePath
+import System.Posix.Redirect
+
+main :: IO ()
+main = byPred assert "false" id False $ do
+    defaultMainWithHooksArgs simpleUserHooks
+        { buildHook = hook }
+        [ "build", "--ghc-option=-ddump-rule-firings" ]
+    putStrLn "http://youtu.be/HOLYYYsFqcI"
+
+hook :: PackageDescription -> LocalBuildInfo -> UserHooks -> BuildFlags -> IO ()
+hook pd lbi uh bf = do
+    forM_ ["hi", "o"] $ \ suf -> removeFile $
+        buildDir lbi </> "rewrite" </> "rewrite-tmp" </> "Main" <.> suf
+    (err, (out, _)) <- redirectStderr . redirectStdout $
+        buildHook simpleUserHooks pd lbi uh bf
+    let combined = err ++ out
+    unless ("Rule fired: assertMessage" `elem` lines combined) $ do
+        putStr combined
+        putStrLn "Rule NOT fired: assertMessage"
+        exitWith (ExitFailure 1)
+