70 lines
2.2 KiB
C
70 lines
2.2 KiB
C
/* mpq_inv(dest,src) -- invert a rational number, i.e. set DEST to SRC
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with the numerator and denominator swapped.
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Copyright 1991, 1994, 1995, 2000, 2001 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or (at your
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option) any later version.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the GNU MP Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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MA 02110-1301, USA. */
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#include "gmp.h"
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#include "gmp-impl.h"
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void
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mpq_inv (MP_RAT *dest, const MP_RAT *src)
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{
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mp_size_t num_size = src->_mp_num._mp_size;
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mp_size_t den_size = src->_mp_den._mp_size;
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if (num_size == 0)
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DIVIDE_BY_ZERO;
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if (num_size < 0)
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{
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num_size = -num_size;
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den_size = -den_size;
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}
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dest->_mp_den._mp_size = num_size;
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dest->_mp_num._mp_size = den_size;
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/* If dest == src we may just swap the numerator and denominator, but
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we have to ensure the new denominator is positive. */
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if (dest == src)
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{
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mp_size_t alloc = dest->_mp_num._mp_alloc;
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mp_ptr limb_ptr = dest->_mp_num._mp_d;
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dest->_mp_num._mp_alloc = dest->_mp_den._mp_alloc;
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dest->_mp_num._mp_d = dest->_mp_den._mp_d;
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dest->_mp_den._mp_alloc = alloc;
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dest->_mp_den._mp_d = limb_ptr;
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}
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else
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{
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den_size = ABS (den_size);
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if (dest->_mp_num._mp_alloc < den_size)
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_mpz_realloc (&(dest->_mp_num), den_size);
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if (dest->_mp_den._mp_alloc < num_size)
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_mpz_realloc (&(dest->_mp_den), num_size);
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MPN_COPY (dest->_mp_num._mp_d, src->_mp_den._mp_d, den_size);
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MPN_COPY (dest->_mp_den._mp_d, src->_mp_num._mp_d, num_size);
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}
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}
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