Re: integer exponentiation with negative exponent

[Coda Highland <chighland@...>]

On Fri, Apr 11, 2014 at 9:05 PM, Peng Zhicheng
<pengzhicheng1986@gmail.com> wrote:
> It may be faster. but it is the semantic difference that I was concerned.
> I suppose the pow function would quite usually overflow a integer(even
> 64-bit long),
> do we really need a dedicated `pow' for integers?

Consider (this is Lua 5.1):

> x = 2^56
> y = x + 1
> =x
7.2057594037928e+16
> =y
7.2057594037928e+16
> =x == y
true

The actual value is 72057594037927936. This is an exact number, with
no precision loss, but the float version gets it wrong.

Now, I don't have 5.3work installed, but I do have Python, which uses
integer exponentiation:

>>> x = 2**56
>>> y = x + 1
>>> x
72057594037927936
>>> y
72057594037927937
>>> x == y
False

5.3work SHOULD give exactly the same results.

/s/ Adam