Re: Pass int64

Theres a few ways you can check it. if you dont need to resolve 
overloads you can just check if its a udata and leave it at that.
but if someone ever passes a different udata type (say another luabind 
object) then itll crash without much helpful information.
To be safer Id say to stash my metatable in the registry under a known 
fixed key and compare it against that.

I tried registering __int64 as a luabind::class_ and it didnt work.
but the alternative (and probably what Id do If we did this again) would 
be to make a light wrapper class and use that.
Its easier to work with than the converter method.
eg if you have register a function that takes __int64 params or returns 
them then you need to have your converter #included or you get the 
"tried to use an unregistered type" error at runtime.



Valery wrote:
> Hello,
>  
> 2 Daniel Wallin:
> Thanks for your sample. I am using LUA with 32 bit integers. Using 
> your version of default_converter<int64>, I may read values as int64 
> in my cpp functions. Yes, this sample does not fully support __int64, 
> but the sample is really useful for me.
>  
> 2 Niki Bowe:
> Thanks for your sample. This seems fully support __int64. I merged it 
> with Daniel's sample (I use new luabind version) and the result worked 
> for me.
> But how to check that metatable is correct? I know this does not 
> relates to luabind, but could you please provide a sample?
>  
> Thanks,
> Valery.
>  
> ----- Original Message -----
> *From:* Niki Bowe <mailto:[email protected]>
> *To:* [email protected] 
> <mailto:[email protected]>
> *Sent:* Monday, June 01, 2009 5:33 AM
> *Subject:* Re: [luabind] Pass int64
>
>
> James Porter wrote:
>> Niki Bowe wrte:
>>   
>>> Done correctly that is the best solution. Itll allow you to do 
>>> arithmetic on 64 bit integers in lua.
>>> Though there is a bit more to it than that.
>>> lua_Number will need to be able to hold int64 values without loss.
>>> which means youll need to either go with int64 as lua_Number (ie integer 
>>> only lua)
>>> or long double as lua_Number (non portable. no guarantee it can 
>>> represent all 64 bit ints.
>>>     
>>
>> Are you sure about this? Because that would imply that Lua 5.1 doesn't 
>> work properly when compiled for a 64-bit platform since, by default, 
>> LUA_INTEGER is #defined to ptrdiff_t. That seems like something the Lua 
>> developers would have considered, but maybe not...
>>
>> - Jim
>>   
> Lua certainly works on 64 bit platforms.
> It just doesnt do what you might expect. depending on what you expect.
>
> The problem here is that lua_Number (by default) is set to double.
> and internally lua values are represented by the following union
> /*
> ** Union of all Lua values
> */
> typedef union {
>   GCObject *gc;
>   void *p;
>   lua_Number n;
>   int b;
> } Value;
>
> Internally when you push an integer it casts it to lua_Number. (see 
> the code for lua_pushinteger).
> So if you want to be able to represent any 64 bit integer in lua you 
> will have to do one of the things I suggested in a previous email.
>
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