[erlang-questions] (Non)Parametrized modules, inheritance, and R15B02 issues?

Yurii Rashkovskii <>
Mon Oct 15 00:43:51 CEST 2012


It is still a question whether the underlying mechanism is to stay. I 
certainly hope it is.

On Sunday, October 14, 2012 2:55:43 PM UTC-7, Erik Søe Sørensen wrote:
>
> Given that the underlying mechanism stays, and only the syntactical 
> conveniences are under threat: to what extent can the current pmod handling 
> be replaced by / emulated with a parse_transform?
> If it's possible to do it that way, that might provide the best of two 
> worlds: the existence of the pmod feature without having the maintenance 
> burden in the compiler.
> Den 12/10/2012 10.04 skrev "Gleb Peregud" < <javascript:>
> >:
>
>> On Thu, Oct 11, 2012 at 11:52 PM, Evan Miller <<javascript:>> 
>> wrote:
>> > I designed BossDB around parameterized modules because pmods allow one
>> > to develop with a familiar ORM pattern in Erlang. I wanted a
>> > record-oriented API that was simple, succinct, and comprehensible.
>> > With pmods I was able to succeed in these goals. For example, to
>> > create a new record:
>> >
>> >   Person = person:new(id, "Joe", "Armstrong")
>> >
>> > To save it:
>> >
>> >    case Person:save() of
>> >        {ok, SavedPerson} -> % do something ...
>> >        {error, ValidationErrors} -> % do something else ...
>> >    end
>> >
>> > To access an attribute:
>> >
>> >    Person:first_name().
>> >    "Joe"
>> >
>> >    Person:last_name().
>> >    "Armstrong"
>>
>> I believe that someone from OTP team mentioned that the parametrized
>> modules are to be deleted, but tuple modules will stay. Essentially
>> this will mean that instead of writing:
>>
>> -module(person, [FirstName, LastName]).
>> -compile(export_all).
>> first_name() ->
>>   FirstName.
>>
>> You will have to write:
>>
>> -module(person).
>> -record(person, {first_name, last_name}).
>> -compile(export_all).
>> new(FirstName, LastName) ->
>>   #person{first_name = FirstName, last_name = LastName}.
>> first_name(Person) ->
>>   Perosn#person.first_name.
>>
>> but you will still be able to do:
>>
>>    Person = person:new("Joe", "Armstrong").
>>    Person:first_name().
>>    "Joe"
>>    case Person:save() of
>>        {ok, SavedPerson} -> % do something ...
>>        {error, ValidationErrors} -> % do something else ...
>>    end.
>>
>> So from point of view of readability there will be no change,
>> althought the amount of code in the model module (person.erl) will
>> slightly increase.
>>
>> Please correct me if I am wrong.
>>
>> Cheers,
>> Gleb
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>>
>
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