diff --git a/cabal.project.local b/cabal.project.local
--- a/cabal.project.local
+++ b/cabal.project.local
@@ -2,3 +2,5 @@
 tests: true
 benchmarks: true
 optimization: 1
+constraints: recursion-schemes -template-haskell
+           , comonad -test-doctests
diff --git a/continued-fraction.cabal b/continued-fraction.cabal
--- a/continued-fraction.cabal
+++ b/continued-fraction.cabal
@@ -1,6 +1,6 @@
 cabal-version: 1.18
 name: continued-fraction
-version: 0.1.0.8
+version: 0.1.0.9
 license: BSD3
 license-file: LICENSE
 copyright: Copyright: (c) 2018 Vanessa McHale
diff --git a/src/Num/ContinuedFraction.hs b/src/Num/ContinuedFraction.hs
--- a/src/Num/ContinuedFraction.hs
+++ b/src/Num/ContinuedFraction.hs
@@ -10,9 +10,11 @@
     , prettyFracM
     ) where
 
-import           Data.Functor.Foldable (ListF (..), apo)
+import           Data.Foldable
+import           Data.Functor.Base
+import           Data.Functor.Foldable (ListF (..), apo, cata)
 import           Data.List             (intersperse)
-import           Data.List.NonEmpty    (NonEmpty (..), fromList)
+import           Data.List.NonEmpty    (NonEmpty (..))
 import           Data.Maybe            (fromJust)
 import           Data.Ratio            (Ratio, denominator, (%))
 
@@ -28,7 +30,7 @@
         idem = ((==) <*>)
         down = realToFrac . (floor :: (RealFrac a) => a -> Integer)
 
--- | This take a number and returns its continued fraction expansion as a list of `Integer`s.
+-- | This take a number and returns its continued fraction expansion as a list of integers.
 --
 -- >>> continuedFraction 2
 -- [2]
@@ -41,12 +43,12 @@
                         go    = Cons (floor x)
 
 prettyFrac :: (Show a) => NonEmpty a -> String
-prettyFrac (x :| xs) = "[" ++ show x ++ "; " ++ mconcat (intersperse ", " (show <$> xs)) ++ "]"
+prettyFrac (x :| xs) = "[" ++ show x ++ "; " ++ fold (intersperse ", " (show <$> xs)) ++ "]"
 
 -- | Print a list as a continued fraction.
 --
 -- >>> prettyFracM (take 5 $ continuedFraction (sqrt 2))
--- "[1; 2, 2, 2, 2]"
+-- Just "[1; 2, 2, 2, 2]"
 prettyFracM :: (Show a) => [a] -> Maybe String
 prettyFracM []     = Nothing
 prettyFracM (x:xs) = Just (prettyFrac (x :| xs))
@@ -57,7 +59,7 @@
 -- Nothing
 -- >>> collapseFractionM [1,2,2,2]
 -- Just (17 % 12)
-collapseFractionM :: (Integral a) => [Integer] -> Maybe (Ratio a)
+collapseFractionM :: (Integral a, Integral b) => [a] -> Maybe (Ratio b)
 collapseFractionM []     = Nothing
 collapseFractionM (x:xs) = Just $ collapseFraction (x:|xs)
 
@@ -66,19 +68,22 @@
 -- >>> collapseFraction (1 :| [2,2,2])
 -- 17 % 12
 collapseFraction :: (Integral a, Integral b) => NonEmpty b -> Ratio a
-collapseFraction (x:|[]) = fromIntegral x % 1
-collapseFraction (x:|xs) = (fromIntegral x % 1) + 1 / collapseFraction (fromList xs)
+collapseFraction = cata a
+    where a (NonEmptyF x xs) = go xs $ fromIntegral x % 1
+          go = maybe id ((+) . (1/))
 
 -- | Find a given convergent of the continued fraction expansion of a number
 --
 -- >>> convergent 4 $ sqrt 2
 -- 17 % 12
 convergent :: (RealFrac a, Integral b) => Int -> a -> Ratio b
-convergent n x = fromJust . collapseFractionM $ take n (continuedFraction x)
+convergent n x = fromJust . (collapseFractionM :: Integral a => [Integer] -> Maybe (Ratio a)) $
+    take n (continuedFraction x)
 
 -- | Find the best rational approximation to a number such that the denominator is bounded by a given value.
 --
 -- >>> approximate pi 100
 -- 22 % 7
 approximate :: (RealFrac a, Integral b) => a -> b -> Ratio b
-approximate x d = last . takeWhile ((<= d) . denominator) $ fmap (flip convergent x) [1..]
+approximate x d = last . takeWhile ((<= d) . denominator) $
+    fmap (flip convergent x) [1..]
diff --git a/stack.yaml b/stack.yaml
--- a/stack.yaml
+++ b/stack.yaml
@@ -1,8 +1,12 @@
-resolver: lts-11.3
+---
+resolver: lts-11.7
 packages:
-- '.'
+  - '.'
 extra-deps:
 flags:
-    continued-fraction:
-        development: true
-extra-package-dbs: []
+  continued-fraction:
+    development: true
+  comonad:
+    test-doctests: false
+  recursion-schemes:
+    template-haskell: false