mpz_invert (x, 1, 0)
bodrato at mail.dm.unipi.it
bodrato at mail.dm.unipi.it
Thu Mar 1 17:33:01 CET 2012
Ciao,
Il Gio, 1 Marzo 2012 4:23 pm, Joerg Arndt ha scritto:
> If mod zero is allowed at all it should
> return the first argument unchanged:
> mod(x,0) = x for all x
>
> So the behavior below is what I would expect.
Maybe you are right, but ...
I did not specify that for any non-unity value n, the current mpz_invert,
returns "non invertible" for the modulus 0.
Moreover the old documentation promised to return an inverse r so that
0<=r<m, where m is the modulus. If m=0, no return value r is allowed by
this restriction: mod zero should not be allowed at all.
I recently changed the documentation writing "0<r<m", but I now realize
that I should change it again, because a negative modulus is allowed:
"0<r<|m|"
Regards, m
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