Bit flip only function?

[Torbjörn Granlund]

Viktor Kletzhändler <vkletzhaendler at swissonline.ch> writes:

  mpz_com seems to do more than flipping. 
  
We might not understand what "flipping" might mean.  mpz_com
computes the one's complement.

  For example, for a base-2 number
  mpz_com ( 1111 1111 ) returns ( -1 0000 0000 )
  whereas I would like _dcom ( 1111 1111 ) returns ( 0 ).
  
  Am I missing something?
  
So "flipping" means f(11111111) = 0, i.e., 8 consecutive ones should map
to 0.  I assume the function "flipping" should be a bijection, so no
other value x should have f(x) = 0.  Perhaps f(f(x)) = x should hold for
any value x?

Then, what should f(1), f(11), f(111), ... yield?  What's so special
about 11111111?

-- 
Torbjörn
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