diff --git a/.hlint.yaml b/.hlint.yaml
new file mode 100644
--- /dev/null
+++ b/.hlint.yaml
@@ -0,0 +1,12 @@
+- arguments: [--cpp-define=HLINT, --cpp-ansi]
+
+# not viable
+- ignore: {name: Reduce duplication}
+
+# don't want to!
+- ignore: {name: Use infix}
+
+# these don't consider the corner cases when using doubles
+- ignore: {name: "Use >"}
+- ignore: {name: "Use <="}
+- ignore: {name: "Use >="}
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
--- a/.travis.yml
+++ /dev/null
@@ -1,121 +0,0 @@
-# This file has been generated -- see https://github.com/hvr/multi-ghc-travis
-language: c
-sudo: false
-
-cache:
-  directories:
-    - $HOME/.cabsnap
-    - $HOME/.cabal/packages
-
-before_cache:
-  - rm -fv $HOME/.cabal/packages/hackage.haskell.org/build-reports.log
-  - rm -fv $HOME/.cabal/packages/hackage.haskell.org/00-index.tar
-
-matrix:
-  include:
-    - env: CABALVER=1.24 GHCVER=7.0.4
-      compiler: ": #GHC 7.0.4"
-      addons: {apt: {packages: [cabal-install-1.24,ghc-7.0.4], sources: [hvr-ghc]}}
-    - env: CABALVER=1.24 GHCVER=7.2.2
-      compiler: ": #GHC 7.2.2"
-      addons: {apt: {packages: [cabal-install-1.24,ghc-7.2.2], sources: [hvr-ghc]}}
-    - env: CABALVER=1.24 GHCVER=7.4.2
-      compiler: ": #GHC 7.4.2"
-      addons: {apt: {packages: [cabal-install-1.24,ghc-7.4.2], sources: [hvr-ghc]}}
-    - env: CABALVER=1.24 GHCVER=7.6.3
-      compiler: ": #GHC 7.6.3"
-      addons: {apt: {packages: [cabal-install-1.24,ghc-7.6.3], sources: [hvr-ghc]}}
-    - env: CABALVER=1.24 GHCVER=7.8.4
-      compiler: ": #GHC 7.8.4"
-      addons: {apt: {packages: [cabal-install-1.24,ghc-7.8.4], sources: [hvr-ghc]}}
-    - env: CABALVER=1.24 GHCVER=7.10.3
-      compiler: ": #GHC 7.10.3"
-      addons: {apt: {packages: [cabal-install-1.24,ghc-7.10.3], sources: [hvr-ghc]}}
-    - env: CABALVER=1.24 GHCVER=8.0.2
-      compiler: ": #GHC 8.0.2"
-      addons: {apt: {packages: [cabal-install-1.24,ghc-8.0.2], sources: [hvr-ghc]}}
-    - env: CABALVER=2.0 GHCVER=8.2.1
-      compiler: ": #GHC 8.2.1"
-      addons: {apt: {packages: [cabal-install-2.0,ghc-8.2.1], sources: [hvr-ghc]}}
-    - env: CABALVER=head GHCVER=head
-      compiler: ": #GHC head"
-      addons: {apt: {packages: [cabal-install-head,ghc-head], sources: [hvr-ghc]}}
-
-  allow_failures:
-    - env: CABALVER=1.24 GHCVER=7.0.4
-    - env: CABALVER=1.24 GHCVER=7.2.2
-    - env: CABALVER=head GHCVER=head
-
-before_install:
- - unset CC
- - export PATH=/opt/ghc/$GHCVER/bin:/opt/cabal/$CABALVER/bin:$PATH
-
-install:
- - cabal --version
- - echo "$(ghc --version) [$(ghc --print-project-git-commit-id 2> /dev/null || echo '?')]"
- - if [ -f $HOME/.cabal/packages/hackage.haskell.org/00-index.tar.gz ];
-   then
-     zcat $HOME/.cabal/packages/hackage.haskell.org/00-index.tar.gz >
-          $HOME/.cabal/packages/hackage.haskell.org/00-index.tar;
-   fi
- - travis_retry cabal update -v
- - sed -i 's/^jobs:/-- jobs:/' ${HOME}/.cabal/config
- - cabal install --only-dependencies --enable-tests --dry -v > installplan.txt
- - sed -i -e '1,/^Resolving /d' installplan.txt; cat installplan.txt
-
-# check whether current requested install-plan matches cached package-db snapshot
- - if diff -u installplan.txt $HOME/.cabsnap/installplan.txt;
-   then
-     echo "cabal build-cache HIT";
-     rm -rfv .ghc;
-     cp -a $HOME/.cabsnap/ghc $HOME/.ghc;
-     cp -a $HOME/.cabsnap/lib $HOME/.cabsnap/share $HOME/.cabsnap/bin $HOME/.cabal/;
-   else
-     echo "cabal build-cache MISS";
-     rm -rf $HOME/.cabsnap;
-     mkdir -p $HOME/.ghc $HOME/.cabal/lib $HOME/.cabal/share $HOME/.cabal/bin;
-     cabal install -j --only-dependencies --enable-tests;
-   fi
-
-# snapshot package-db on cache miss
- - if [ ! -d $HOME/.cabsnap ];
-   then
-      echo "snapshotting package-db to build-cache";
-      mkdir $HOME/.cabsnap;
-      cp -a $HOME/.ghc $HOME/.cabsnap/ghc;
-      cp -a $HOME/.cabal/lib $HOME/.cabal/share $HOME/.cabal/bin installplan.txt $HOME/.cabsnap/;
-   fi
-
-# Here starts the actual work to be performed for the package under
-# test; any command which exits with a non-zero exit code causes the
-# build to fail.
-script:
- # -v2 provides useful information for debugging
- - cabal configure --enable-tests -v2
-
- # this builds all libraries and executables
- # (including tests/benchmarks)
- - cabal build
-
- # tests that a source-distribution can be generated
- - cabal sdist
-
- # check that the generated source-distribution can be built & installed
- - export SRC_TGZ=$(cabal info . | awk '{print $2 ".tar.gz";exit}') ;
-   cd dist/;
-   if [ -f "$SRC_TGZ" ]; then
-      cabal install --force-reinstalls "$SRC_TGZ";
-   else
-      echo "expected '$SRC_TGZ' not found";
-      exit 1;
-   fi
-
-notifications:
-  irc:
-    channels:
-      - "irc.freenode.org#haskell-lens"
-    skip_join: true
-    template:
-      - "\x0313intervals\x03/\x0306%{branch}\x03 \x0314%{commit}\x03 %{build_url} %{message}"
-
-# EOF
diff --git a/CHANGELOG.markdown b/CHANGELOG.markdown
--- a/CHANGELOG.markdown
+++ b/CHANGELOG.markdown
@@ -1,3 +1,26 @@
+0.9.3 [2024.12.04]
+------------------
+* Drop support for pre-8.0 versions of GHC.
+
+0.9.2 [2021.02.17]
+------------------
+* Export `(/=!)` and `(/=?)` operators.
+* The build-type has been changed from `Custom` to `Simple`.
+  To achieve this, the `doctests` test suite has been removed in favor of using
+  [`cabal-docspec`](https://github.com/phadej/cabal-extras/tree/master/cabal-docspec)
+  to run the doctests.
+
+0.9.1 [2020.01.29]
+------------------
+* Add `Semigroup` instances for the `Interval` types in `Numeric.Interval`,
+  `Numeric.Interval.Kaucher`, and `Numeric.Interval.NonEmpty`.
+  Add a `Monoid` instance for the `Interval` type in `Numeric.Interval`.
+
+0.9 [2019.05.10]
+----------------
+* Remove the `Foldable` instances for the `Interval` types from
+  `Numeric.Interval` and `Numeric.Interval.NonEmpty`.
+
 0.8.1
 -----
 * Support `doctest-0.12`
diff --git a/HLint.hs b/HLint.hs
deleted file mode 100644
--- a/HLint.hs
+++ /dev/null
@@ -1,12 +0,0 @@
-import "hint" HLint.HLint
-
--- not viable
-ignore "Reduce duplication"
-
--- don't want to!
-ignore "Use infix"
-
--- these don't consider the corner cases when using doubles
-ignore "Use >"
-ignore "Use <="
-ignore "Use >="
diff --git a/README.markdown b/README.markdown
--- a/README.markdown
+++ b/README.markdown
@@ -1,7 +1,7 @@
 intervals
 ==========
 
-[![Hackage](https://img.shields.io/hackage/v/intervals.svg)](https://hackage.haskell.org/package/intervals) [![Build Status](https://secure.travis-ci.org/ekmett/intervals.svg?branch=master)](http://travis-ci.org/ekmett/intervals)
+[![Hackage](https://img.shields.io/hackage/v/intervals.svg)](https://hackage.haskell.org/package/intervals) [![Build Status](https://github.com/ekmett/intervals/workflows/Haskell-CI/badge.svg)](https://github.com/ekmett/intervals/actions?query=workflow%3AHaskell-CI)
 
 Basic interval arithmetic
 
diff --git a/Setup.lhs b/Setup.lhs
--- a/Setup.lhs
+++ b/Setup.lhs
@@ -1,34 +1,7 @@
-\begin{code}
-{-# LANGUAGE CPP #-}
-{-# OPTIONS_GHC -Wall #-}
-module Main (main) where
-
-#ifndef MIN_VERSION_cabal_doctest
-#define MIN_VERSION_cabal_doctest(x,y,z) 0
-#endif
-
-#if MIN_VERSION_cabal_doctest(1,0,0)
-
-import Distribution.Extra.Doctest ( defaultMainWithDoctests )
-main :: IO ()
-main = defaultMainWithDoctests "doctests"
-
-#else
-
-#ifdef MIN_VERSION_Cabal
--- If the macro is defined, we have new cabal-install,
--- but for some reason we don't have cabal-doctest in package-db
---
--- Probably we are running cabal sdist, when otherwise using new-build
--- workflow
-import Warning ()
-#endif
-
-import Distribution.Simple
-
-main :: IO ()
-main = defaultMain
+#!/usr/bin/runhaskell
+> module Main (main) where
 
-#endif
+> import Distribution.Simple
 
-\end{code}
+> main :: IO ()
+> main = defaultMain
diff --git a/Warning.hs b/Warning.hs
deleted file mode 100644
--- a/Warning.hs
+++ /dev/null
@@ -1,5 +0,0 @@
-module Warning
-  {-# WARNING ["You are configuring this package without cabal-doctest installed.",
-               "The doctests test-suite will not work as a result.",
-               "To fix this, install cabal-doctest before configuring."] #-}
-  () where
diff --git a/intervals.cabal b/intervals.cabal
--- a/intervals.cabal
+++ b/intervals.cabal
@@ -1,5 +1,5 @@
 name:              intervals
-version:           0.8.1
+version:           0.9.3
 synopsis:          Interval Arithmetic
 description:
   A 'Numeric.Interval.Interval' is a closed, convex set of floating point values.
@@ -15,33 +15,29 @@
 author:             Edward Kmett
 maintainer:         ekmett@gmail.com
 category:           Math
-build-type:         Custom
-cabal-version:      >=1.8
-tested-with:        GHC == 7.4.2, GHC == 7.6.1, GHC == 7.6.3, GHC == 7.8.4, GHC == 7.10.3, GHC == 8.0.2, GHC == 8.2.1
+build-type:         Simple
+cabal-version:      >=1.10
+tested-with:        GHC == 8.0.2
+                  , GHC == 8.2.2
+                  , GHC == 8.4.4
+                  , GHC == 8.6.5
+                  , GHC == 8.8.4
+                  , GHC == 8.10.7
+                  , GHC == 9.0.2
+                  , GHC == 9.2.8
+                  , GHC == 9.4.8
+                  , GHC == 9.6.6
+                  , GHC == 9.8.4
+                  , GHC == 9.10.1
 extra-source-files:
-  .travis.yml
+  .hlint.yaml
   CHANGELOG.markdown
   README.markdown
-  HLint.hs
-  Warning.hs
 
 source-repository head
   type: git
   location: git://github.com/ekmett/intervals.git
 
-custom-setup
-  setup-depends:
-    base >= 4 && <5,
-    Cabal,
-    cabal-doctest >= 1 && <1.1
-
--- You can disable the doctests test suite with -f-test-doctests
-flag test-doctests
-  description: Enable (or disable via f-test-doctests) the doctest suite when
-               using the enable-tests option for cabal.
-  default: True
-  manual: True
-
 flag herbie
   default: False
   manual: True
@@ -59,11 +55,9 @@
 
   build-depends:
     array          >= 0.3   && < 0.6,
-    base           >= 4     && < 5,
-    distributive   >= 0.2   && < 1
-
-  if impl(ghc >=7.4)
-    build-depends: ghc-prim
+    base           >= 4.9   && < 5,
+    distributive   >= 0.2   && < 1,
+    ghc-prim
 
   ghc-options:     -Wall -O2
 
@@ -72,21 +66,15 @@
     cpp-options: -DHERBIE
     ghc-options: -fplugin=Herbie
 
+  default-language: Haskell2010
+  x-docspec-options: --check-properties
+  x-docspec-property-variables: i x y xs ys
 
 test-suite doctests
   type:           exitcode-stdio-1.0
   main-is:        doctests.hs
   ghc-options:    -Wall -threaded
   hs-source-dirs: tests
-
-  if !flag(test-doctests)
-    buildable: False
-  else
-    build-depends:
-      base,
-      directory      >= 1.0,
-      doctest        >= 0.11.1 && <0.13,
-      filepath,
-      intervals,
-      QuickCheck,
-      template-haskell
+  build-depends:  base >= 4.9 && < 5
+                , QuickCheck >=2.14.2
+  default-language: Haskell2010
diff --git a/src/Numeric/Interval.hs b/src/Numeric/Interval.hs
--- a/src/Numeric/Interval.hs
+++ b/src/Numeric/Interval.hs
@@ -38,8 +38,8 @@
   , scale, symmetric
   , contains
   , isSubsetOf
-  , certainly, (<!), (<=!), (==!), (>=!), (>!)
-  , possibly, (<?), (<=?), (==?), (>=?), (>?)
+  , certainly, (<!), (<=!), (==!), (/=!), (>=!), (>!)
+  , possibly, (<?), (<=?), (==?), (/=?), (>=?), (>?)
   , idouble
   , ifloat
   , iquot
diff --git a/src/Numeric/Interval/Exception.hs b/src/Numeric/Interval/Exception.hs
--- a/src/Numeric/Interval/Exception.hs
+++ b/src/Numeric/Interval/Exception.hs
@@ -8,7 +8,7 @@
 import Data.Data
 
 data EmptyInterval = EmptyInterval
-  deriving (Eq,Ord,Typeable,Data)
+  deriving (Eq,Ord,Data)
 
 instance Show EmptyInterval where
   show EmptyInterval = "empty interval"
@@ -16,7 +16,7 @@
 instance Exception EmptyInterval
 
 data AmbiguousComparison = AmbiguousComparison
-  deriving (Eq,Ord,Typeable,Data)
+  deriving (Eq,Ord,Data)
 
 instance Show AmbiguousComparison where
   show AmbiguousComparison = "ambiguous comparison"
diff --git a/src/Numeric/Interval/Internal.hs b/src/Numeric/Interval/Internal.hs
--- a/src/Numeric/Interval/Internal.hs
+++ b/src/Numeric/Interval/Internal.hs
@@ -1,9 +1,7 @@
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE Rank2Types #-}
 {-# LANGUAGE DeriveDataTypeable #-}
-#if __GLASGOW_HASKELL__ >= 704
 {-# LANGUAGE DeriveGeneric #-}
-#endif
 {-# OPTIONS_HADDOCK not-home #-}
 -----------------------------------------------------------------------------
 -- |
@@ -46,8 +44,8 @@
   , scale, symmetric
   , contains
   , isSubsetOf
-  , certainly, (<!), (<=!), (==!), (>=!), (>!)
-  , possibly, (<?), (<=?), (==?), (>=?), (>?)
+  , certainly, (<!), (<=!), (==!), (/=!), (>=!), (>!)
+  , possibly, (<?), (<=?), (==?), (/=?), (>=?), (>?)
   , idouble
   , ifloat
   , iquot
@@ -58,37 +56,30 @@
 
 import Control.Exception as Exception
 import Data.Data
-import Data.Foldable hiding (minimum, maximum, elem, notElem
-#if __GLASGOW_HASKELL__ >= 710
-  , null
-#endif
-  )
 import Data.Function (on)
-import Data.Monoid
-#if __GLASGOW_HASKELL__ >= 704
 import GHC.Generics
-#endif
 import Numeric.Interval.Exception
 import Prelude hiding (null, elem, notElem)
 
+import qualified Data.Semigroup
+import qualified Data.Monoid
+
 -- $setup
+-- >>> :set -Wno-deprecations
+-- >>> let null = Numeric.Interval.Internal.null
+-- >>> let elem = Numeric.Interval.Internal.elem
+-- >>> let notElem = Numeric.Interval.Internal.notElem
 
 data Interval a = I !a !a | Empty deriving
-  ( Eq, Ord
-  , Data
-  , Typeable
-#if __GLASGOW_HASKELL__ >= 704
-  , Generic
-#if __GLASGOW_HASKELL__ >= 706
-  , Generic1
-#endif
-#endif
-  )
+  (Eq, Ord, Data, Generic, Generic1)
 
-instance Foldable Interval where
-  foldMap f (I a b) = f a `mappend` f b
-  foldMap _ Empty = mempty
-  {-# INLINE foldMap #-}
+-- | 'Data.Semigroup.<>' is 'hull'
+instance Ord a => Data.Semigroup.Semigroup (Interval a) where
+  (<>) = hull
+
+instance Ord a => Data.Monoid.Monoid (Interval a) where
+  mempty = empty
+  mappend = (Data.Semigroup.<>)
 
 infix 3 ...
 infixl 6 +/-
diff --git a/src/Numeric/Interval/Kaucher.hs b/src/Numeric/Interval/Kaucher.hs
--- a/src/Numeric/Interval/Kaucher.hs
+++ b/src/Numeric/Interval/Kaucher.hs
@@ -1,9 +1,7 @@
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE Rank2Types #-}
 {-# LANGUAGE DeriveDataTypeable #-}
-#if __GLASGOW_HASKELL__ >= 704
 {-# LANGUAGE DeriveGeneric #-}
-#endif
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Numeric.Interval
@@ -44,8 +42,8 @@
   , scale, symmetric
   , contains
   , isSubsetOf
-  , certainly, (<!), (<=!), (==!), (>=!), (>!)
-  , possibly, (<?), (<=?), (==?), (>=?), (>?)
+  , certainly, (<!), (<=!), (==!), (/=!), (>=!), (>!)
+  , possibly, (<?), (<=?), (==?), (/=?), (>=?), (>?)
   , clamp
   , idouble
   , ifloat
@@ -59,40 +57,35 @@
 import Control.Exception as Exception
 import Data.Data
 import Data.Distributive
-import Data.Foldable hiding (minimum, maximum, elem, notElem
-#if __GLASGOW_HASKELL__ >= 710
-  , null
-#endif
-  )
+import Data.Foldable hiding (minimum, maximum, elem, notElem, null)
 import Data.Function (on)
-import Data.Monoid
 import Data.Traversable
-#if __GLASGOW_HASKELL__ >= 704
 import GHC.Generics
-#endif
 import Numeric.Interval.Exception
 import Prelude hiding (null, elem, notElem)
 
+import qualified Data.Semigroup
+import qualified Data.Monoid
+
 -- $setup
+-- >>> :set -Wno-deprecations
+-- >>> let null = Numeric.Interval.Kaucher.null
+-- >>> let elem = Numeric.Interval.Kaucher.elem
+-- >>> let notElem = Numeric.Interval.Kaucher.notElem
 
 data Interval a = I !a !a deriving
-  ( Eq, Ord
-  , Data
-  , Typeable
-#if __GLASGOW_HASKELL__ >= 704
-  , Generic
-#if __GLASGOW_HASKELL__ >= 706
-  , Generic1
-#endif
-#endif
-  )
+  (Eq, Ord, Data, Generic, Generic1)
 
+-- | 'Data.Semigroup.<>' is 'hull'
+instance Ord a => Data.Semigroup.Semigroup (Interval a) where
+  (<>) = hull
+
 instance Functor Interval where
   fmap f (I a b) = I (f a) (f b)
   {-# INLINE fmap #-}
 
 instance Foldable Interval where
-  foldMap f (I a b) = f a `mappend` f b
+  foldMap f (I a b) = f a `Data.Monoid.mappend` f b
   {-# INLINE foldMap #-}
 
 instance Traversable Interval where
@@ -106,8 +99,10 @@
   {-# INLINE (<*>) #-}
 
 instance Monad Interval where
+#if !(MIN_VERSION_base(4,11,0))
   return a = I a a
   {-# INLINE return #-}
+#endif
   I a b >>= f = I a' b' where
     I a' _ = f a
     I _ b' = f b
@@ -662,6 +657,10 @@
 --
 -- >>> hull (15 ... 85 :: Interval Double) (0 ... 10 :: Interval Double)
 -- 0.0 ... 85.0
+--
+-- >>> hull (10 ... 20 :: Interval Double) (15 ... 0 :: Interval Double)
+-- 10.0 ... 20.0
+--
 hull :: Ord a => Interval a -> Interval a -> Interval a
 hull x@(I a b) y@(I a' b')
   | null x = y
diff --git a/src/Numeric/Interval/NonEmpty.hs b/src/Numeric/Interval/NonEmpty.hs
--- a/src/Numeric/Interval/NonEmpty.hs
+++ b/src/Numeric/Interval/NonEmpty.hs
@@ -1,9 +1,6 @@
-{-# LANGUAGE CPP #-}
 {-# LANGUAGE Rank2Types #-}
 {-# LANGUAGE DeriveDataTypeable #-}
-#if __GLASGOW_HASKELL__ >= 704
 {-# LANGUAGE DeriveGeneric #-}
-#endif
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Numeric.Interval.NonEmpty
@@ -41,8 +38,8 @@
   , mignitude
   , contains
   , isSubsetOf
-  , certainly, (<!), (<=!), (==!), (>=!), (>!)
-  , possibly, (<?), (<=?), (==?), (>=?), (>?)
+  , certainly, (<!), (<=!), (==!), (/=!), (>=!), (>!)
+  , possibly, (<?), (<=?), (==?), (/=?), (>=?), (>?)
   , clamp
   , inflate, deflate
   , scale, symmetric
diff --git a/src/Numeric/Interval/NonEmpty/Internal.hs b/src/Numeric/Interval/NonEmpty/Internal.hs
--- a/src/Numeric/Interval/NonEmpty/Internal.hs
+++ b/src/Numeric/Interval/NonEmpty/Internal.hs
@@ -1,9 +1,7 @@
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE Rank2Types #-}
 {-# LANGUAGE DeriveDataTypeable #-}
-#if __GLASGOW_HASKELL__ >= 704
 {-# LANGUAGE DeriveGeneric #-}
-#endif
 {-# OPTIONS_HADDOCK not-home #-}
 -----------------------------------------------------------------------------
 -- |
@@ -40,8 +38,8 @@
   , mignitude
   , contains
   , isSubsetOf
-  , certainly, (<!), (<=!), (==!), (>=!), (>!)
-  , possibly, (<?), (<=?), (==?), (>=?), (>?)
+  , certainly, (<!), (<=!), (==!), (/=!), (>=!), (>!)
+  , possibly, (<?), (<=?), (==?), (/=?), (>=?), (>?)
   , clamp
   , inflate, deflate
   , scale, symmetric
@@ -55,19 +53,17 @@
 
 import Control.Exception as Exception
 import Data.Data
-import Data.Foldable hiding (minimum, maximum, elem, notElem)
-import Data.Monoid
-#if __GLASGOW_HASKELL__ >= 704
 import GHC.Generics
-#endif
-import Numeric.Interval.Exception
 import Prelude hiding (null, elem, notElem)
 
+import qualified Data.Semigroup
+
 -- $setup
 -- >>> import Test.QuickCheck.Arbitrary
 -- >>> import Test.QuickCheck.Gen hiding (scale)
 -- >>> import Test.QuickCheck.Property
 -- >>> import Control.Applicative
+-- >>> import Control.Exception
 -- >>> :set -XNoMonomorphismRestriction
 -- >>> :set -XExtendedDefaultRules
 -- >>> default (Integer,Double)
@@ -78,22 +74,17 @@
 -- >>> let conservativeExceptNaN sf f xs = forAll (choose (inf xs, sup xs)) $ \x -> isNaN (sf x) || (sf x) `member` (f xs)
 -- >>> let compose2 = fmap . fmap
 -- >>> let commutative op a b = (a `op` b) == (b `op` a)
+--
+-- >>> :set -Wno-deprecations
+-- >>> let elem = Numeric.Interval.NonEmpty.Internal.elem
+-- >>> let notElem = Numeric.Interval.NonEmpty.Internal.notElem
 
 data Interval a = I !a !a deriving
-  ( Eq, Ord
-  , Data
-  , Typeable
-#if __GLASGOW_HASKELL__ >= 704
-  , Generic
-#if __GLASGOW_HASKELL__ >= 706
-  , Generic1
-#endif
-#endif
-  )
+  (Eq, Ord, Data, Generic, Generic1)
 
-instance Foldable Interval where
-  foldMap f (I a b) = f a `mappend` f b
-  {-# INLINE foldMap #-}
+-- | 'Data.Semigroup.<>' is 'hull'
+instance Ord a => Data.Semigroup.Semigroup (Interval a) where
+  (<>) = hull
 
 infix 3 ...
 
@@ -432,8 +423,9 @@
 
 -- | Fractional instance for intervals.
 --
--- prop> ys /= singleton 0 ==> conservative2 ((/) :: Double -> Double -> Double) (/) xs ys
--- prop> xs /= singleton 0 ==> conservative (recip :: Double -> Double) recip xs
+-- -- The property tests below are currently disabled (#66).
+-- -- prop> ys /= singleton 0 ==> conservative2 ((/) :: Double -> Double -> Double) (/) xs ys
+-- -- prop> xs /= singleton 0 ==> conservative (recip :: Double -> Double) recip xs
 instance (Fractional a, Ord a) => Fractional (Interval a) where
   -- TODO: check isNegativeZero properly
   x / y@(I a b)
@@ -492,7 +484,7 @@
   cos = periodic (2 * pi) (symmetric 1) (signum' . negate . sin) cos
   tan = periodic pi       whole         (const GT)               tan -- derivative only has to have correct sign
   asin (I a b) = (asin' a) ... (asin' b)
-    where 
+    where
       asin' x | x >= 1 = halfPi
               | x <= -1 = -halfPi
               | otherwise = asin x
@@ -801,7 +793,8 @@
 -- >>> scale (-2.0) (-1.0 ... 1.0)
 -- -2.0 ... 2.0
 --
--- prop> abs x >= 1 ==> (scale (x :: Double) i) `contains` i
+-- -- The property test below is currently disabled (#66).
+-- -- prop> abs x >= 1 ==> (scale (x :: Double) i) `contains` i
 -- prop> forAll (choose (0,1)) $ \x -> abs x <= 1 ==> i `contains` (scale (x :: Double) i)
 scale :: (Fractional a, Ord a) => a -> Interval a -> Interval a
 scale x i = a ... b where
diff --git a/tests/doctests.hs b/tests/doctests.hs
--- a/tests/doctests.hs
+++ b/tests/doctests.hs
@@ -7,19 +7,13 @@
 -- Stability   :  provisional
 -- Portability :  portable
 --
--- This module provides doctests for a project based on the actual versions
--- of the packages it was built with. It requires a corresponding Setup.lhs
--- to be added to the project
+-- This module exists to add dependencies
 -----------------------------------------------------------------------------
 module Main where
 
-import Build_doctests (flags, pkgs, module_sources)
-import Data.Foldable (traverse_)
-import Test.DocTest
-
 main :: IO ()
 main = do
-    traverse_ putStrLn args
-    doctest args
-  where
-    args = flags ++ pkgs ++ module_sources
+    putStrLn "This test-suite exists only to add dependencies"
+    putStrLn "To run doctests: "
+    putStrLn "    cabal build all --enable-tests"
+    putStrLn "    cabal-docspec"