diff --git a/LICENSE b/LICENSE
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--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,30 @@
+Copyright M Farkas-Dyck © 2018
+
+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 M Farkas-Dyck 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/README.md b/README.md
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--- /dev/null
+++ b/README.md
@@ -0,0 +1,1 @@
+# ival
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/ival.cabal b/ival.cabal
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--- /dev/null
+++ b/ival.cabal
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+name:                ival
+version:             0.1.0.0
+synopsis:            Intervals
+-- description:
+license:             BSD3
+license-file:        LICENSE
+author:              M Farkas-Dyck
+maintainer:          strake888@gmail.com
+copyright:           2018 Target Corporation
+-- category:            
+build-type:          Simple
+extra-source-files:  README.md
+cabal-version:       >=1.10
+
+library
+  hs-source-dirs:      src
+  exposed-modules:     Data.Interval
+  build-depends:       alg >= 0.2.6 && < 0.3
+                     , base >= 4.7 && < 5
+  default-language:    Haskell2010
+  default-extensions:  UnicodeSyntax
+                     , LambdaCase
+                     , EmptyCase
+                     , InstanceSigs
+                     , PartialTypeSignatures
+                     , PolyKinds
+                     , ConstraintKinds
+                     , FlexibleContexts
+                     , FlexibleInstances
+                     , MonadComprehensions
+                     , StandaloneDeriving
+                     , DeriveFunctor, DeriveFoldable, DeriveTraversable
+  ghc-options:         -Wall -Wcompat -Wredundant-constraints -Wno-name-shadowing
+                       -Wincomplete-record-updates -Wincomplete-uni-patterns
+                       -Werror=incomplete-patterns
+                       -Werror=incomplete-uni-patterns
+                       -Werror=incomplete-record-updates
+                       -Werror=missing-fields
+                       -Werror=missing-methods
+
+test-suite test
+  type:                exitcode-stdio-1.0
+  hs-source-dirs:      test
+  main-is:             Main.hs
+  build-depends:       base >=4.11 && <5
+                     , smallcheck >=1.1.4
+                     , tasty >=1.0
+                     , tasty-smallcheck >=0.8
+                     , ival
+  default-language:    Haskell2010
+  default-extensions:  UnicodeSyntax
+                     , LambdaCase
+                     , EmptyCase
+                     , InstanceSigs
+                     , PartialTypeSignatures
+                     , PolyKinds
+                     , ConstraintKinds
+                     , FlexibleContexts
+                     , FlexibleInstances
+                     , MonadComprehensions
+                     , StandaloneDeriving
+                     , DeriveFunctor, DeriveFoldable, DeriveTraversable
+  ghc-options:         -Wall -Wcompat -Wredundant-constraints -Wno-name-shadowing
+                       -Wincomplete-record-updates -Wincomplete-uni-patterns
+                       -Werror=incomplete-patterns
+                       -Werror=incomplete-uni-patterns
+                       -Werror=incomplete-record-updates
+                       -Werror=missing-fields
+                       -Werror=missing-methods
+
+source-repository head
+  type:     git
+  location: https://github.com/strake/ival.hs
diff --git a/src/Data/Interval.hs b/src/Data/Interval.hs
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--- /dev/null
+++ b/src/Data/Interval.hs
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+module Data.Interval (Interval (..), (∪), (∩)) where
+
+import Prelude hiding (Eq, Ord (..), max, min)
+
+import Control.Applicative
+import Data.Function (on)
+import Data.Ord (Down (..))
+import Relation.Binary.Comparison
+
+infix 5 :–:
+data Interval a = Maybe a :–: Maybe a
+    deriving (Read, Show,
+              Functor, Foldable, Traversable)
+
+instance Preord a => Preord (Interval a) where
+    a₁ :–: b₁ ≤ a₂ :–: b₂ = Lexical a₁ ≤ Lexical b₁ && ((≥) `on` Down . Lexical . fmap Down) a₂ b₂
+instance PartialEq a => PartialEq (Interval a) where a₁ :–: b₁ ≡ a₂ :–: b₂ = (a₁, b₁) ≡ (a₂, b₂)
+instance (PartialOrd a, PartialEq a) => PartialOrd (Interval a)
+instance Eq a => Eq (Interval a)
+
+infixr 4 ∪, ∩
+(∪), (∩) :: Ord a => Interval a -> Interval a -> Interval a
+a₁ :–: b₁ ∪ a₂ :–: b₂ = liftA2 min a₁ a₂ :–: liftA2 max b₁ b₂
+a₁ :–: b₁ ∩ a₂ :–: b₂ = fmap unMax (fmap Max a₁ <> fmap Max a₂) :–:
+                        fmap unMin (fmap Min b₁ <> fmap Min b₂)
diff --git a/test/Main.hs b/test/Main.hs
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--- /dev/null
+++ b/test/Main.hs
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+module Main where
+
+import Test.SmallCheck
+import Test.Tasty
+import Test.Tasty.SmallCheck
+
+main :: IO ()
+main = defaultMain $ testGroup "" []