inv.c
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上传日期:2022-08-06
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- /* mpq_inv(dest,src) -- invert a rational number, i.e. set DEST to SRC
- with the numerator and denominator swapped.
- Copyright 1991, 1994, 1995, 2000, 2001 Free Software Foundation, Inc.
- This file is part of the GNU MP Library.
- The GNU MP Library is free software; you can redistribute it and/or modify
- it under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 3 of the License, or (at your
- option) any later version.
- The GNU MP Library is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
- License for more details.
- You should have received a copy of the GNU Lesser General Public License
- along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
- #include "gmp.h"
- #include "gmp-impl.h"
- void
- mpq_inv (MP_RAT *dest, const MP_RAT *src)
- {
- mp_size_t num_size = src->_mp_num._mp_size;
- mp_size_t den_size = src->_mp_den._mp_size;
- if (num_size == 0)
- DIVIDE_BY_ZERO;
- if (num_size < 0)
- {
- num_size = -num_size;
- den_size = -den_size;
- }
- dest->_mp_den._mp_size = num_size;
- dest->_mp_num._mp_size = den_size;
- /* If dest == src we may just swap the numerator and denominator, but
- we have to ensure the new denominator is positive. */
- if (dest == src)
- {
- mp_size_t alloc = dest->_mp_num._mp_alloc;
- mp_ptr limb_ptr = dest->_mp_num._mp_d;
- dest->_mp_num._mp_alloc = dest->_mp_den._mp_alloc;
- dest->_mp_num._mp_d = dest->_mp_den._mp_d;
- dest->_mp_den._mp_alloc = alloc;
- dest->_mp_den._mp_d = limb_ptr;
- }
- else
- {
- den_size = ABS (den_size);
- if (dest->_mp_num._mp_alloc < den_size)
- _mpz_realloc (&(dest->_mp_num), den_size);
- if (dest->_mp_den._mp_alloc < num_size)
- _mpz_realloc (&(dest->_mp_den), num_size);
- MPN_COPY (dest->_mp_num._mp_d, src->_mp_den._mp_d, den_size);
- MPN_COPY (dest->_mp_den._mp_d, src->_mp_num._mp_d, num_size);
- }
- }