diff --git a/pos.cabal b/pos.cabal
--- a/pos.cabal
+++ b/pos.cabal
@@ -5,7 +5,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           pos
-version:        0.1.0.0
+version:        0.2.0.0
 synopsis:       positive numbers
 description:    A library for representing positive integers. . Useful for handling nonempty containers and fixed containers.
 category:       Data, Numeric
diff --git a/src/Data/Pos.hs b/src/Data/Pos.hs
--- a/src/Data/Pos.hs
+++ b/src/Data/Pos.hs
@@ -2,8 +2,8 @@
 {-# LANGUAGE ConstraintKinds #-}
 {-# LANGUAGE DataKinds #-}
 {-# LANGUAGE DerivingStrategies #-}
-{-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE PatternSynonyms #-}
 {-# LANGUAGE ScopedTypeVariables #-}
@@ -74,7 +74,7 @@
   type PosT,
   fromN,
   fromNP,
-  NSC (..),
+  NS (..),
 
   -- ** miscellaneous
 
@@ -277,20 +277,23 @@
   FailUnless 'False err = GL.TypeError ( 'GL.Text "FailUnless: " 'GL.:<>: err)
   FailUnless 'True _ = ()
 
--- | conversion from nonempty list of Nats to Positives
-type NSC :: NonEmpty Nat -> Constraint
-class NSC ns where
+-- | conversion from list of Nats to Positives
+type NS :: [Nat] -> Constraint
+class NS ns where
   fromNSP :: NonEmpty Pos
   fromNSTotalP :: Pos
   fromNSTotalP = productP (fromNSP @ns)
   nsLengthP :: Pos
 
-instance PosT n => NSC (n ':| '[]) where
+instance GL.TypeError ( 'GL.Text "NS: empty dimensions are not supported") => NS '[] where
+  fromNSP = error "fromNSP: should not be here"
+  nsLengthP = error "fromNSP: should not be here"
+instance PosT n => NS '[n] where
   fromNSP = fromNP @n :| []
   nsLengthP = _1P
-instance (PosT n, NSC (n1 ':| ns)) => NSC (n ':| n1 ': ns) where
-  fromNSP = fromNP @n N.<| fromNSP @(n1 ':| ns)
-  nsLengthP = succP (nsLengthP @(n1 ':| ns))
+instance (PosT n, NS (n1 ': ns)) => NS (n ': n1 ': ns) where
+  fromNSP = fromNP @n N.<| fromNSP @(n1 ': ns)
+  nsLengthP = succP (nsLengthP @(n1 ': ns))
 
 -- | construct a valid 'Pos' using a 'Nat'
 _P :: forall n. PosT n => Pos
diff --git a/test/Main.hs b/test/Main.hs
--- a/test/Main.hs
+++ b/test/Main.hs
@@ -3,7 +3,6 @@
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeApplications #-}
-{-# LANGUAGE TypeOperators #-}
 
 module Main where
 
@@ -43,8 +42,8 @@
     , testCase "reads space between" $ reads @Pos " 9 P" @?= []
     , testCase "reads leading spaces and extra" $ reads @Pos " 9P xyz" @?= [(_9P, " xyz")]
     , testCase "reads leading spaces and extra" $ reads @Pos "   123P" @?= [(_P @123, "")]
-    , testCase "fromNSP" $ fromNSP @(4 ':| '[]) @?= (_4P :| [])
-    , testCase "fromNSP" $ fromNSP @(4 ':| '[6, 3]) @?= (_4P :| [_6P, _3P])
+    , testCase "fromNSP" $ fromNSP @'[4] @?= (_4P :| [])
+    , testCase "fromNSP" $ fromNSP @'[4, 6, 3] @?= (_4P :| [_6P, _3P])
     , testCase "fromNP 1" $ fromNP @1 @?= _1P
     , testCase "fromNP 2" $ fromNP @2 @?= _2P
     , testCase "fromNP 3" $ fromNP @3 @?= _3P
@@ -68,10 +67,10 @@
     , testCase "fromN 4" $ fromN @4 @?= 4
     , testCase "fromN 1" $ fromN @1 @?= 1
     , testCase "fromNSTotalP" $
-        fromNSTotalP @(2 ':| '[3, 20])
+        fromNSTotalP @'[2, 3, 20]
           @?= _P @120
     , testCase "fromNSP" $
-        fromNSP @(2 ':| '[3, 20])
+        fromNSP @'[2, 3, 20]
           @?= _2P :| [_3P, _20P]
     , testCase "pPosInt" $
         P.readP_to_S pPosInt "  12xyz"