diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+0.1.3.0: [2018.05.23]
+---------------------
+* remove dependency on `constrictor`.
+* some doc fixes.
+
 0.1.2: [2018.05.04]
 -------------------
 * `semirings` now builds back to
diff --git a/Data/Semiring.hs b/Data/Semiring.hs
--- a/Data/Semiring.hs
+++ b/Data/Semiring.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE BangPatterns               #-}
 {-# LANGUAGE CPP                        #-}
 {-# LANGUAGE DefaultSignatures          #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
@@ -29,9 +30,6 @@
   , minus 
   ) where 
 
-#if defined(VERSION_constrictor)
-import           Constrictor (Ap(..))
-#endif
 import           Control.Applicative (Alternative(..), Applicative(..), Const(..), liftA2)
 import           Data.Bool (Bool(..), (||), (&&), otherwise, not)
 import           Data.Complex (Complex(..))
@@ -177,8 +175,8 @@
 -- can think of a semiring as two monoids of the same
 -- underlying type: A commutative monoid and an
 -- associative monoid. For any type R with a 'Prelude.Num'
--- instance, the commutative monoid is (R, '(Prelude.+)', 0)
--- and the associative monoid is (R, '(Prelude.*)', 1).
+-- instance, the commutative monoid is (R, 'GHC.Num.+', 0)
+-- and the associative monoid is (R, 'GHC.Num.*', 1).
 --
 -- Instances should satisfy the following laws:
 --
@@ -204,25 +202,30 @@
 -- 
 -- [/left- and right-distributivity of '*' over '+'/]
 --
---     @x '*' (y '+' z) = (x '*' y) '+' (x '*' z)@
---     @(x '+' y) '*' z = (x '*' z) '+' (y '*' z)@
+--     @
+--     x '*' (y '+' z) = (x '*' y) '+' (x '*' z)
+--     (x '+' y) '*' z = (x '*' z) '+' (y '*' z)
+--     @
 --
 -- [/annihilation/]
 --
 --     @'zero' '*' x = x '*' 'zero' = 'zero'@
+--
 
 class Semiring a where
+#if __GLASGOW_HASKELL__ >= 708
   {-# MINIMAL plus, zero, times, one #-}
+#endif
   plus  :: a -> a -> a -- ^ Commutative Operation
   zero  :: a           -- ^ Commutative Unit
   times :: a -> a -> a -- ^ Associative Operation
   one   :: a           -- ^ Associative Unit
 
   -- useful for defining semirings over ground types
-  default zero  :: Num.Num a => a -- ^ 0
-  default one   :: Num.Num a => a -- ^ 1
-  default plus  :: Num.Num a => a -> a -> a -- ^ '(Prelude.+)'
-  default times :: Num.Num a => a -> a -> a -- ^ '(Prelude.*)'
+  default zero  :: Num.Num a => a
+  default one   :: Num.Num a => a
+  default plus  :: Num.Num a => a -> a -> a
+  default times :: Num.Num a => a -> a -> a
   zero  = 0
   one   = 1
   plus  = (Num.+)
@@ -233,14 +236,16 @@
 --     @'negate' a '+' a = 'zero'@
 
 class Semiring a => Ring a where
+#if __GLASGOW_HASKELL__ >= 708
   {-# MINIMAL negate #-}
+#endif
   negate :: a -> a
 
   default negate :: Num.Num a => a -> a
   negate = Num.negate
 
 -- | Substract two 'Ring' values. For any type 'R' with
--- a 'Prelude.Num' instance, this is the same as '(Prelude.-)'.
+-- a 'Prelude.Num' instance, this is the same as Prelude's 'GHC.Num.-'.
 --
 --     @x `minus` y = x '+' 'negate' y@
 minus :: Ring a => a -> a -> a
@@ -498,18 +503,6 @@
 deriving instance Ring a => Ring (Max a)
 deriving instance Ring a => Ring (Min a)
 instance HasResolution a => Ring (Fixed a)
-
-{--------------------------------------------------------------------
-  Instances (constrictor)
---------------------------------------------------------------------}
-
-#if defined(VERSION_constrictor)
-instance (Applicative f, Semiring a) => Semiring (Ap f a) where
-  zero  = Ap (pure zero)
-  one   = Ap (pure one)
-  plus  = liftA2 plus
-  times = liftA2 times
-#endif
 
 {--------------------------------------------------------------------
   Instances (containers)
diff --git a/semirings.cabal b/semirings.cabal
--- a/semirings.cabal
+++ b/semirings.cabal
@@ -1,6 +1,6 @@
 name:          semirings
 category:      Algebra, Data, Data Structures, Math, Maths, Mathematics
-version:       0.1.2
+version:       0.1.3.0
 license:       BSD3
 cabal-version: >= 1.10
 license-file:  LICENSE
@@ -49,14 +49,6 @@
   default: True
   manual: True
 
-flag constrictor
-  description:
-    You can disable the use of the `constrictor` package using `-f-constrictor`.
-    .
-    Disabling this may be useful for accelerating builds in sandboxes for expert users.
-    default: True
-    manual: True
-
 flag containers
   description:
     You can disable the use of the `containers` package using `-f-containers`.
@@ -88,11 +80,14 @@
   build-depends:
       base >= 4.5 && < 5
     , integer-gmp
-    , semigroups
-    , transformers
   
   if impl(ghc < 7.10)
-    build-depends: nats >= 0.1 && < 2
+    build-depends:
+        nats >= 0.1 && < 2
+      , transformers
+
+  if impl(ghc < 8.0)
+    build-depends: semigroups
     
   if impl(ghc >= 7.2)
     exposed-modules:
@@ -101,9 +96,6 @@
   if impl(ghc >= 7.6.1)
     exposed-modules:
       Data.Semiring.Generic
-    
-    if flag(constrictor)
-      build-depends: constrictor >= 0.1.1.1 && < 0.2.0.0
     
     if flag(containers)
       build-depends: containers >= 0.3 && < 0.6