anchor.diff:  			     {{N, RData}, <<>>} = protobuffs:decode(list_to_binary(Bin), Type),
       			 in_range(Data,Type) andalso
       			     FieldNum=:=N andalso
  -    			     (Data==RData orelse foreign_type(Type,Data,RData))  
  +    			     (compare(Data,RData) orelse foreign_type(Type,Data,RData))
   	     end).
   
   prop_encode_decode() ->
  
positive.code: 	             {field_num(), uint(64),uint64},
  	             {field_num(), bool(),bool},
                   {field_num(), sint(32),sint32},
  		         {field_num(), sint(64),sint64}])).
  
  field_num() ->
      ?SUCHTHAT(N,nat(),N>0).
  
negative.code:     	    begin
          		{{N, RData}, <<>>} = protobuffs:decode(list_to_binary(protobuffs:encode(FieldNum, Data, Type)), Type),
          		FieldNum=:=N andalso 
          		(compare(Data,RData) orelse foreign_type(Type,Data,RData))  
      	    end
  	    )).
  
  