On 12/3/18, Magicks M <m4gicks@gmail.com> wrote:
> Quoting from Programming in lua:
>
>> We can write constants larger than 2^63 -1 directly, despite appearances:
>>
> > x = 13835058055282163712 -- 3 << 62
>>
> > x --> -4611686018427387904
>>
> When I enter this example into an interpreter (you can try in the lua demo)
> the number is cast to a float, is that supposed to happen?
Since this numeric constant has neither radix point nor exponent, and
does not fit in an integer, it is not defined by the manual (§3.1):
> A numeric constant with a radix point or an exponent denotes a float; otherwise, if its value fits in an integer, it denotes an integer.
The claim in PIL is consistent with 5.3.0-2, but changed in 5.3.3. The
manual text in that section is the same. Of course, pre-5.3 versions
generally have the "new" behaviour due to using only floating-point
numbers.
But this integer exists ! The _expression_ (-2147483647 - 1) uses only integers within the positive subset, and produces an integer, even if its negation would produce a double with the Lua operator. This is the only integer (assuming integers are 32 bits) that has no distinct negation as an integer.
If integers are compiled as 64-bit (normally the case on 64-bit target architecture where the C "int" type is 64-bit), then the unique integer without distinct negation is (-9223372036854775807-1).
You may still have not understood this issue.