Re: Custom type methods (and name)

[Ivan <ivan@...>]

19.02.2016, 08:14, "Dirk Laurie" <dirk.laurie@gmail.com>:
> 2016-02-18 22:46 GMT+02:00 Ivan <ivan@sleepyiora.pw>:
>>  I’m trying to create my own type (for complex numbers) and
>>  use it within Lua scripts.
>
> This has been done by Luiz himself (Google: complex lua lhf).

Ok, but complex is not the only custom type I need. 

>
>>  It’s okay but the problem is that in some messages this type is
>>  denoted as ‘userdata’ which looks ugly. I have found that if type’s
>>  metatable has __name field, that it’s value is used as a type name.
>>  Unfortunately this key is not used everywhere, e.g. pairs(complex)
>>  still uses ‘userdata’ name. Is there a way I can make Lua to use
>>  custom type name?
>
> Under Lua 5.3.2 with Luiz's complex, I get:
>
>>  z=complex.new(0,1); pairs(z)
>
> stdin:1: bad argument #1 to 'pairs' (table expected, got complex number)
>
> So I can't reproduce your result.
>
> The manual says only:
>
>     The entry __name is used by some error-reporting functions.
>
> The word "some" usually means "at least one but not all". I suspect
> that the vagueness is deliberate, and if you could provide a list of
> which error messages you would like to have included too, some (!)
> might get into Lua 5.3.3.

My code:

local cx = complex.new(0, 0)

local cx2 = complex.new(1, 1)

print(cx < cx2)

and the mesasge 'attempt to compare two userdata values'

It seems that I have to implement all of the metamethods (even those that are not supported by the domain) nad provide my own error messages.

-- -- 

And still I'm looking for a way to use both OOP style (my_array:length()) and array-style (my_array[1] = 0)