diff --git a/LICENSE b/LICENSE
new file mode 100644
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,30 @@
+Copyright (c) 2016, Athan Clark
+
+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 Athan Clark 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/src/Data/Unfoldable/Restricted.hs b/src/Data/Unfoldable/Restricted.hs
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--- /dev/null
+++ b/src/Data/Unfoldable/Restricted.hs
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+{-# LANGUAGE
+    KindSignatures
+  , ConstraintKinds
+  , MultiParamTypeClasses
+  , FunctionalDependencies
+  , FlexibleInstances
+  #-}
+
+module Data.Unfoldable.Restricted where
+
+import Data.Unfolder        (Unfolder (choose))
+import Data.Constraint      (Constraint)
+import Data.Constraint.Unit (Unit)
+
+import qualified Data.Set as Set
+import qualified Data.Map as Map
+
+import qualified Data.HashMap.Lazy as HashMap
+import qualified Data.HashSet      as HashSet
+
+import Data.Hashable (Hashable)
+
+
+class UnfoldableR
+        (pred :: * -> Constraint)
+        (t :: * -> *)
+      | t -> pred where
+  unfoldRestrict :: (pred a, Unfolder f) => f a -> f (t a)
+
+class BiUnfoldableR
+        (predA :: * -> Constraint)
+        (predB :: * -> Constraint)
+        (t :: * -> * -> *)
+      | t -> predA predB where
+  biunfoldRestrict :: (predA a, predB b, Unfolder f) => f a -> f b -> f (t a b)
+
+
+-- Containers
+
+instance UnfoldableR (Ord) Set.Set where
+  unfoldRestrict fa = choose
+    [ pure Set.empty
+    , Set.singleton <$> fa
+    , Set.union <$> unfoldRestrict fa <*> unfoldRestrict fa
+    ]
+
+instance BiUnfoldableR (Ord) Unit Map.Map where
+  biunfoldRestrict fa fb = choose
+    [ pure Map.empty
+    , Map.singleton <$> fa <*> fb
+    , Map.union <$> biunfoldRestrict fa fb <*> biunfoldRestrict fa fb
+    ]
+
+
+-- Unordered Containers
+
+
+class (Hashable a, Eq a) => Hashable' a
+
+instance UnfoldableR (Hashable') HashSet.HashSet where
+  unfoldRestrict fa = choose
+    [ pure HashSet.empty
+    , HashSet.singleton <$> fa
+    , HashSet.union <$> unfoldRestrict fa <*> unfoldRestrict fa
+    ]
+
+instance BiUnfoldableR (Hashable') (Unit) HashMap.HashMap where
+  biunfoldRestrict fa fb = choose
+    [ pure HashMap.empty
+    , HashMap.singleton <$> fa <*> fb
+    , HashMap.union <$> biunfoldRestrict fa fb <*> biunfoldRestrict fa fb
+    ]
diff --git a/unfoldable-restricted.cabal b/unfoldable-restricted.cabal
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--- /dev/null
+++ b/unfoldable-restricted.cabal
@@ -0,0 +1,26 @@
+Name:                   unfoldable-restricted
+Version:                0.0.0
+Author:                 Athan Clark <athan.clark@gmail.com>
+Maintainer:             Athan Clark <athan.clark@gmail.com>
+License:                BSD3
+License-File:           LICENSE
+Synopsis:               An alternative to the Unfoldable typeclass
+Cabal-Version:          >= 1.10
+Build-Type:             Simple
+
+Library
+  Default-Language:     Haskell2010
+  HS-Source-Dirs:       src
+  GHC-Options:          -Wall
+  Exposed-Modules:      Data.Unfoldable.Restricted
+  Build-Depends:        base >= 4.8 && < 5
+                      , constraints
+                      , containers
+                      , hashable
+                      , unfoldable
+                      , unit-constraint
+                      , unordered-containers
+
+Source-Repository head
+  Type:                 git
+  Location:             git@github.com:athanclark/unfoldable-restricted.git