[erlang-questions] Basic Erlang case question

[Hynek Vychodil]

It is only warning. You must be sure that all your branches bound variable
or in very rare case you know what you are doing.

On Thu, Jul 10, 2008 at 10:41 AM, Alexander Lamb
<alexander.lamb@REDACTED> wrote:

> Hello List,
>
> Here is a very simple code to search if a supplied password is correct
> or not:
>
>                                F1 = fun() -> mnesia:match_object(systems,
> #system_info{full_attribute = {System_Name,admin_password}, _ = '_'},
> read) end,
>                                case Password of
>                                        [] -> MD5_Password = [];
>                                        _Any -> MD5_Password =
> erlang:md5(Password)
>                                end,


% It will remove warning message.
MD5_Password = case Password of
      [] -> [];
      _ -> erlang:md5(Password)
   end,

>
>                                case mnesia:transaction(F1) of
>                                        {atomic, []}
>                                      -> {error, unknown_system};
>                                        {atomic, [#system_info{data =
> MD5_Password}]} -> {ok, password};
>                                        {atomic, _}
>                                               -> {error, bad_password};
>                                        {aborted, Reason}
>                                       -> {error, Reason}
>                                end
>
>
>
> Basically, if supplied Password is empty, the MD5_Password must be
> empty. If not, I encrypt the Password to compare it with stored version.
>
> My problem is that it compiles with a warning:
>
> ./cs_systems.erl:173: Warning: variable 'MD5_Password' exported from
> 'case' (line 167)
>
> Why? Obviously I am trying to match the password in the record I found
> with the password I supply.
>
> Thanks,
>
> Alex
>
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>



-- 
--Hynek (Pichi) Vychodil
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