anchor.diff:      _ ->
         {error, "Could not find library"}
     end.
  +
  +sha256_init() -> "Undefined".
  
positive.code: 
  %% API exports
  -export([
           sha256_init/0,
           hash_update/2,
           hash_final/1
          ]).
  
negative.code: %% API functions
  %%====================================================================
  
  hash_init(sha256) ->
      sha256_init().
  
  hash_update(_Context, _Data) -> "Undefined".
  hash_final(_Context) -> "Undefined".
  
  