[erlang-questions] Re: Defensive Programming

[Mazen Harake]

I wrote this once... see if it makes sense:
http://mazenharake.wordpress.com/2009/09/14/let-it-crash-the-right-way/

/Mazen


On 17/05/2010 02:12, Henning Diedrich wrote:
> Thanks Steve,
>
> that question of "is it recoverable?" makes a lot of sense to clarify. 
> I am taking note.
>
> In my case I am writing a lib function for others to use, which is 
> exactly why I would like to give them more information on the error.
>
> Even though they might not be able to recover it, they should at least 
> know why it didn't work, instead of just getting a bad match for "ok = "
>
> I meanwhile conclude that the trimmest variant will be to care less 
> and demand that the user of the function test for the return value 
> directly handed over from the gen_tcp:send() call. Making it
>
> login(Name, Password) ->
>
>       ...
>        gen_tcp:send(Socket, term_to_binary(Str)).
>
>
>
> That looks the Erlangest an hands responsibility to the person who can 
> actually answer the 'recoverability question', the user of the lib.
>
> I realize I'd like to take away chances of frustration, puffing it up 
> in the process.
>
> Thanks for taking a look!
> Henning
>
>
>
> Steve Davis wrote:
>> Hi Henning,
>>
>> This isn't intended to be any kind of definite answer, and I'm
>> interested to see how others respond.
>>
>> In my case how I deal with this question is that I'd probably ask
>> myself:
>>
>> *Is this exceptional case _recoverable_,? e.g. in the case of the tcp
>> send, you could try to resend the data, so the first idiom may do it.
>>
>> If it's not recoverable, I'd just let it crash out. In fact I would
>> likely force it to crash out using the second idiom.
>>
>> If I want to get fancy with error handling, I find that try..catch at
>> the top level is usually enough.
>>
>> A further aside to this is that a certain Mr Armstrong once introduced
>> me to an interesting "transactional" idiom also, namely:
>>
>> try begin
>> ...
>> end catch
>> ...
>>
>> Regards,
>>
>> /s
>>
>> On May 16, 5:04 pm, Henning Diedrich <hd2...@REDACTED> wrote:
>>> Hi list,
>>>
>>> I have a question about the Erlang way.
>>>
>>> I realize I keep programming defensive using exceptions/error calls to
>>> *label failure* more precisely.
>>>
>>> E.g. ( - PRESUMABLY WRONG - )
>>>
>>> login(Name, Password) ->
>>>
>>>        ...
>>>         case
>>>                 gen_tcp:send(Socket, term_to_binary(Str)) of
>>>                      ok -> ok;
>>>                      _ -> erlang:error(*sending_failed, {Str }*)
>>>        end
>>>        ...
>>>
>>> Instead of simply
>>>
>>> login(Name, Password) ->
>>>
>>>        ...
>>>         ok = gen_tcp:send(Socket, term_to_binary(Str)),
>>>        ...
>>>
>>> It feels wrong in Erlang and I wonder if I am missing out on something.
>>>
>>> If somebody has a pointer to read up on this, thanks in advance,
>>>
>>> Henning
>>>
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