Re: 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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