[erlang-questions] -spec tuple variable size

Dmitry Kolesnikov <>
Thu Nov 29 17:08:35 CET 2012


Hello,

Yes, you are right that tuples are converted into list during the serialisation process. You cannot avoid it but api offered to client uses tuples. 

- Dmitry

On Nov 29, 2012, at 6:03 PM, Siraaj Khandkar <> wrote:

> I don't know all the technicalities of Erlang's type specs, but in general -
> variable growth is antithetical to the concept of a tuple.
> 
> You'll still need to accumulate the elements in some list before you convert
> it to a tuple, so why not just spec that list?
> 
> 
> On Nov 28, 2012, at 5:10 PM, Dmitry Kolesnikov <> wrote:
> 
>> Hello,
>> 
>> Thanks for response!
>> Let me explain better what I am trying to achieve.
>> "The shorthand [T,...] stands for the set of non-empty proper lists whose elements are of type T." 
>> I am looking for similar definition but for tuples.
>> 
>> My application serialises tuples into disk. The size of tuple is unbound but tuple elements a fixed to string, binary, number, boolean or undefined. I cannot use " "|" operator to define as many variants as you like" because number of variants is unlimited. Well practically, I do have a hard limit of 4096 elements per tuple but I am lazy to type in 4096 variants :-) 
>> 
>> - Dmitry
>> 
>> On Nov 28, 2012, at 11:50 PM, Motiejus Jakštys <> wrote:
>> 
>>> On Wed, Nov 28, 2012 at 9:10 PM, Dmitry Kolesnikov
>>> <> wrote:
>>>> but compiler fails syntax error before: ','
>>>> 
>>>> -- CLIP --
>>>> -type value()     :: string() | binary() | number() | boolean() | undefined.
>>>> -type entity()    :: [{atom(), value()}] | {field()}.
>>> 
>>> These should be fine.
>>> 
>>>> -type field()      :: value() | value(), field().
>>> 
>>> Maybe you meant
>>> -type field() :: value() | {value(), field()}.
>>> 
>>> ?
>>> 
>>> In general, if you want to define tuples of different sizes in -spec,
>>> you use the "|" operator to define as many variants as you like.
>>> 
>>> Likely I don't understand what you are trying to define.
> 
> -- 
> Siraaj Khandkar
> .o.
> ..o
> ooo
> 




More information about the erlang-questions mailing list