How would you solve this 'interview' question in D?

[Marco Leise]

Am Wed, 26 Jun 2013 22:52:17 +0200
schrieb "Gary Willoughby" <dev at kalekold.net>:

> The text from the question:
> 
> Design a function f, such that:
> 
> f(f(n)) == -n
> Where n is a 32 bit signed integer; you can't use complex numbers
> arithmetic.
> 
> If you can't design such a function for the whole range of
> numbers, design it for the largest range possible.

Well some good answers are given that would work in D, too. I
like how this question turns out the nature of the person much
more than their general programming skill. Some options:

o downvote the question and close the tab
o face it with humor (e.g. throw NotImplementedException("You
  get the rest of the code when you give me the job"))
o get dirty and hack around the issue, by actually having two 
  'f's (by means of C preprocessor abuse, or C++ overloads)
o be the pragmatic Python programmer: no overflows, no problems
o adhere strictly to the problem description and give multiple
  solutions that do or don't handle 0 or -2^31.

Anyway I've yet to see a solution that works for all input ;)

-- 
Marco