Vincent Lefevre vincent at
Tue May 7 10:58:59 CEST 2013

On 2013-05-07 10:43:33 +0200, Zimmermann Paul wrote:
> I discovered the mpn_neg function:
>  -- Function: mp_limb_t mpn_neg (mp_limb_t *RP, const mp_limb_t *SP,
>           mp_size_t N)
>      Perform the negation of {SP, N}, and write the result to {RP, N}.
>      Return carry-out.
> Since mpn only deals with nonnegative numbers, what is "the negation of
> {SP, N}"? Also, should the carry be a borrow?

Isn't this the equivalent of mpn_sub_n where the first term of
the subtraction is equal to 0? But for mpn_sub_n, it is said
"borrow" for the returned value.

Vincent Lefèvre <vincent at> - Web: <>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

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