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bundled/Basement/NonEmpty.hs

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+{-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE RebindableSyntax #-}
+{-# LANGUAGE NoImplicitPrelude #-}
+-- |
+-- Module      : Basement.NonEmpty
+-- License     : BSD-style
+-- Maintainer  : Foundation
+-- Stability   : experimental
+-- Portability : portable
+--
+-- A newtype wrapper around a non-empty Collection.
+
+module Basement.NonEmpty
+    ( NonEmpty(..)
+    ) where
+
+import           Basement.Exception
+import           Basement.Compat.Base
+
+-- | NonEmpty property for any Collection
+newtype NonEmpty a = NonEmpty { getNonEmpty :: a }
+    deriving (Show,Eq)
+
+instance IsList c => IsList (NonEmpty c) where
+    type Item (NonEmpty c) = Item c
+    toList      = toList . getNonEmpty
+    fromList [] = throw NonEmptyCollectionIsEmpty
+    fromList l  = NonEmpty . fromList $ l