anchor.diff:  -module('Microsoft.FSharp.Collections.MapModule').
  --compile(export_all).
  +-export([
  +         add/3,
  +         containsKey/2,
  +         empty/0,
  +         exists/2,
  +         filter/2,
  +         find/2,
  +         findKey/2,
  +         fold/3,
  +         % foldBack/3,
  +         % forall/2,
  +         isEmpty/1,
  +         % iter/2,
  +         map/2,
  +         % ofArray/1,
  +         % ofList/1,
  +         % ofSeq/1,
  +         % partition/3,
  +         % pick/2,
  +         remove/2,
  +         % toArray/1,
  +         toList/1,
  +         % toSeq/1,
  +         tryFind/2
  +         % tryFindKey/3,
  +         % tryPick/2
  +        ]).
   
   
   add(K, V, M) ->
  
positive.code: tryFind(K, M) ->
      maps:get(K, M, undefined).
  
  
negative.code:                       F(Acc, K, V)
                end, S, M).
  
  isEmpty(#{}) -> true;
  isEmpty(_) -> false.
  
  