// This is probably for use in Meta_v2 to get the most efficient
// (read compact) implementation of typical meta scenarios.

interface MutatingMap<A, B> {
  Non-mutating:
  
    isEmpty
    size
    entrySet/iterator (I prefer the latter)
    containsKey
    get
    hashCode/equals (of course)
    
  Mutating:
  
    MutatingMap<A, B> put(A a, B b)
    MutatingMap<A, B> remove(O a)
    MutatingMap<A, B> putAll(Map)
    MutatingMap<A, B> putAll(MutatingMap)
    MutatingMap<A, B> clear()
  
}