Re: [Feature Request?] __key

["Soni L." <fakedme@...>]

On 16/07/16 12:15 PM, Philipp Janda wrote:
> Am 16.07.2016 um 16:57 schröbte Soni L.:
> > On 15/07/16 08:05 PM, Tim Hill wrote:
> > > — What is the type of the return value? It can’t be any existing Lua
> > > type, since this is *already* used as the identity of a value of that
> > > type. In other words, if __key returns (say) 100 as the key, then that
> > > will collide with using the number 100 in the same table. Not good. In
> > > fact, the only thing that __key could conceivably return would be
> > > another userdata pointer. And if you analyze this carefully, you will
> > > see if doesn’t buy you any functionality over what you already have.
> >
> > Not good? If you have a bigint with value 100, any reasonable person
> > would expect it to be compatible with a plain Lua number with value 100,
> > just like how the plain Lua integer 100 is compatible with the plain Lua
> > float 100.0. If Lua numbers have this property, why shouldn't other 
> > things?
>
> Doing the interning and equivalence class thing during construction of 
> your bigints instead of during table indexing has the added advantage, 
> that `100 == bigint(100)` works as well, that something like 
> `table.insert({}, bigint(1), x)` works as well, and that it's probably 
> also faster.
>
> Philipp
And then you have bigint(2^62) + bigint(2^62) == bigint(-2^63)

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