IntMapClass experiment

1 files changed, 41 insertions, 0 deletions

diff --git a/IntMapClass.hs b/IntMapClass.hs
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--- /dev/null
+++ b/IntMapClass.hs
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+{-# LANGUAGE CPP,
+             FlexibleContexts,
+             MultiParamTypeClasses,
+             GeneralizedNewtypeDeriving,
+             DeriveDataTypeable #-}
+module IntMapClass where
+
+import qualified Data.IntMap.Strict as IntMap
+import Data.IntMap.Strict ( IntMap )
+import Data.Typeable ( Typeable )
+import Data.Data     ( Data )
+import Data.Foldable ( Foldable )
+import Data.Traversable ( Traversable )
+import Data.Monoid   ( Monoid )
+import Control.DeepSeq ( NFData )
+#if MIN_VERSION_base(4,7,0)
+import Data.Coerce
+#else
+class Coercible a b where coerce :: a -> b
+#endif
+
+newtype IMap k a = IMap (IntMap a)
+ deriving
+    ( Functor
+    , Typeable
+    , Foldable
+    , Traversable
+    , Eq
+    , Data
+    , Ord
+    , Read
+    , Show
+    , Monoid
+    , NFData
+    )
+
+adapt_m_k :: Coercible k Int => (IntMap a -> Int -> x) -> IMap k a -> k -> x
+adapt_m_k f (IMap m) k = f m (coerce k)
+
+(!) :: Coercible k Int => IMap k a -> k -> a
+(!) = adapt_m_k (IntMap.!)