Re: The hypothetical __serialize metamethod (was Re: [ANN] luaproc 1.0-4)

[Coda Highland <chighland@...>]

On Tue, Oct 6, 2015 at 10:15 AM, Sean Conner <sean@conman.org> wrote:
> It was thus said that the Great Andrew Starks once stated:
>> On Tue, Oct 6, 2015 at 11:12 AM, Rena <hyperhacker@gmail.com> wrote:
>> > I think you could use a __serialize metamethod here, when you don't have a
>> > built-in handler. Then userdata, magic tables and other objects could define
>> > handlers as easily as they do other metamethods.
>>
>> I've often used __tostring for this, but then that wrecks my (often
>> needed) method for pretty printing. I'm also guilty(?) of using two
>> underscores, which I believe is, by documentation (?), reserved for
>> the language. But I do it too...
>>
>> Overall, however, a serialize metamethod has been my preferred way of
>> figuring this stuff out. We also found ourselves wanting to know if
>> the message was going inter-process or just inter-thread, but that's
>> too fancy for this purpose.
>
>   But wouldn't there have to be a consensus as to *what* __serialize
> returns?  I mean, obviously, a string of byte values (variation on a string)
> but the actual contents can vary widely.  Given a simple Lua table:
>
>         { 1 , "two" , true }
>
>   One person might want to serialize that as JSON:
>
>         [ 1 , "two" , true ]
>
>   Someone else might want BSON [1] (hex dump follows):
>
>         13 00 00 00 04 00 0D 00
>         00 00 30 00 01 00 00 00
>         31 00 74 77 6F 32 01
>
>   Another one (like me) might want to serialize to CBOR [2] (hex dump
> follows):
>
>         83 01 63 74 77 6F F5
>
> and yet another might want straight up Lua:
>
>         { 1 , "two" , true }
>
>   Is it better to perhaps just reserve "__serialize" for serialization and
> leave it up to modules to flesh it out?  Or do we need to actually define
> the output format?
>
>   -spc (Not a proposal, just something to talk about ... )
>
> [1]     http://bsonspec.org/spec.html
>
> [2]     RFC-7049
>

Solution: Don't call it __serialize! Call it __json, __bson, __cbor,
or whatever's actually appropriate for the format.

You could borrow a Pythonism and use __repr for Lua syntax.

/s/ Adam