diff --git a/LICENSE b/LICENSE
new file mode 100644
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,20 @@
+Copyright (c) 2015 Piotr Młodawski
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be included
+in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
diff --git a/Setup.hs b/Setup.hs
new file mode 100644
--- /dev/null
+++ b/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/error-util.cabal b/error-util.cabal
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--- /dev/null
+++ b/error-util.cabal
@@ -0,0 +1,28 @@
+name:                error-util
+version:             0.0.1.1
+synopsis:            Set of utils and operators for error handling
+description:         Set of utils and operators for error handling
+license:             MIT
+license-file:        LICENSE
+author:              Piotr Młodawski
+maintainer:          Piotr Młodawski <remdezx+github@gmail.com>
+homepage:            http://github.com/pmlodawski/error-util
+bug-reports:         http://github.com/pmlodawski/error-util/issues
+category:            Error Handling
+build-type:          Simple
+tested-with:         GHC == 7.8.4, GHC == 7.10.1, GHC == 7.10.2
+cabal-version:       >=1.10
+
+library
+    exposed-modules:
+        Control.Error.Operator
+    default-language:   Haskell2010
+    build-depends:      base >=4.7 && <4.9,
+                        transformers > 0.4.0.0
+
+    hs-source-dirs:     src
+    default-language:   Haskell2010
+
+source-repository head
+    type:     git
+    location: http://github.com/pmlodawski/error-util.git
diff --git a/src/Control/Error/Operator.hs b/src/Control/Error/Operator.hs
new file mode 100644
--- /dev/null
+++ b/src/Control/Error/Operator.hs
@@ -0,0 +1,64 @@
+{-# LANGUAGE FlexibleContexts #-}
+
+module Control.Error.Operator (
+    module Control.Error.Operator,
+    module X,
+) where
+
+import           Control.Monad              (unless)
+import           Control.Monad.Trans.Except as X
+import qualified Data.Maybe                 as Maybe
+import           Prelude
+
+
+--------------------------------------------------------------------------------
+-- Either operators using `Left` to raise error
+--------------------------------------------------------------------------------
+
+infixl 4 <?>
+(<?>) :: Maybe b -> a -> Either a b
+val <?> m = Maybe.maybe (Left m) Right val
+
+infixl 4 <?&>
+(<?&>) :: Either a (Maybe b) -> a -> Either a b
+val <?&> m = Maybe.maybe (Left m) Right =<< val
+
+--------------------------------------------------------------------------------
+-- ExceptT operators using `throwE` to raise error
+--------------------------------------------------------------------------------
+
+infixl 4 <??>
+(<??>) :: Monad m => Maybe b -> a -> ExceptT a m b
+val <??> m = Maybe.maybe (throwE m) return val
+
+infixl 4 <??&>
+(<??&>) :: Monad m => ExceptT a m (Maybe b) -> a -> ExceptT a m b
+val <??&> m = Maybe.maybe (throwE m) return =<< val
+
+--------------------------------------------------------------------------------
+-- Simple monadic operators using `fail` to raise error
+--------------------------------------------------------------------------------
+
+infixl 4 <?.>
+(<?.>) :: Monad m => Maybe b -> String -> m b
+val <?.> m = Maybe.maybe (fail m) return val
+
+infixl 4 <?&.>
+(<?&.>) :: Monad m => m (Maybe b) -> String -> m b
+val <?&.> m = Maybe.maybe (fail m) return =<< val
+
+--------------------------------------------------------------------------------
+-- Assertions
+--------------------------------------------------------------------------------
+
+-- | assert in `Either` monad, using `Left` to raise error
+assert :: Bool -> a -> Either a ()
+assert condition msg = unless condition $ Left msg
+
+-- | assert in `ExceptT` monad, using `throwE` to raise error
+assertE :: Monad m => Bool -> a -> ExceptT a m ()
+assertE condition msg = unless condition $ throwE msg
+
+-- | assert in any monad, using `fail` to raise error
+assertM :: Monad m => Bool -> String -> m ()
+assertM condition msg = unless condition $ fail msg