ziv@2203: functor MultimapFn (structure KeyMap : ORD_MAP structure ValSet : ORD_SET) = struct
ziv@2203:     type key = KeyMap.Key.ord_key
ziv@2203:     type item = ValSet.item
ziv@2203:     type items = ValSet.set
ziv@2203:     type multimap = ValSet.set KeyMap.map
ziv@2203:     fun inserts (kToVs : multimap, k : key, vs : items) : multimap =
ziv@2203:         KeyMap.unionWith ValSet.union (kToVs, KeyMap.singleton (k, vs))
ziv@2203:     fun insert (kToVs : multimap, k : key, v : item) : multimap =
ziv@2203:         inserts (kToVs, k, ValSet.singleton v)
ziv@2203:     fun find (kToVs : multimap, k : key) =
ziv@2203:         case KeyMap.find (kToVs, k) of
ziv@2203:             SOME vs => vs
ziv@2203:           | NONE => ValSet.empty
ziv@2203: end