module Data.Map.Util where
import Data.Map (Map)
import qualified Data.Map as M
type Tag = Int
type Index = Int
nextLowerTag, nextHigherTag :: Map Tag a -> Tag
nextLowerTag = maybe 0 pred . minTag
nextHigherTag = maybe 0 succ . maxTag
minTag, maxTag :: Map Tag a -> Maybe Tag
minTag m = fst . fst <$> M.minViewWithKey m
maxTag m = fst . fst <$> M.maxViewWithKey m
showsPrecList :: Show a => (b -> [a]) -> Int -> b -> ShowS
showsPrecList toList d o = showParen (d > 10) $
showString "fromList " . shows (toList o)
readsPrecList :: Read a => ([a] -> b) -> Int -> ReadS b
readsPrecList fromList d = readParen (d > 10) $ \r -> do
("fromList", s) <- lex r
(xs, t) <- reads s
return (fromList xs, t)