module PropertyMap(ReadPropertyMap(..), 
		   ReadWritePropertyMap(..),
		   FMap, init_map, create_map, fmap_to_list) where

  import FiniteMap

  class ReadPropertyMap pmap key value
    | pmap -> key, pmap -> value where
    get :: pmap -> key -> value
  
  class ReadPropertyMap pmap key value =>
      ReadWritePropertyMap pmap key value where
    put :: pmap -> key -> value -> pmap


  data FMap key elt = FinMap (FiniteMap key elt) elt

  init_map :: Ord key =>
      [key] -> value -> FMap key value
  init_map keys val
      = FinMap (listToFM [(k,val) | k <- keys ]) val

  create_map :: Ord key =>
      [(key,value)] -> value -> FMap key value
  create_map alist val = FinMap (listToFM alist) val

  fmap_to_list :: FMap key value -> [(key,value)]
  fmap_to_list (FinMap fm elt) = fmToList fm

  instance Ord key =>
      ReadPropertyMap (FMap key elt) key elt where
    get (FinMap fmap e) k = lookupWithDefaultFM fmap e k

  instance Ord key =>
      ReadWritePropertyMap (FMap key elt) key elt where
    put (FinMap fmap e) k v =
	(FinMap (addToFM (delFromFM fmap k) k v) e)