75 lines
2.0 KiB
C
75 lines
2.0 KiB
C
/* mpq_inv(dest,src) -- invert a rational number, i.e. set DEST to SRC
|
|
with the numerator and denominator swapped.
|
|
|
|
Copyright (C) 1991 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 General Public License as published by
|
|
the Free Software Foundation; either version 2, 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 General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with the GNU MP Library; see the file COPYING. If not, write to
|
|
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
|
|
|
|
#include "gmp.h"
|
|
#include "gmp-impl.h"
|
|
|
|
void
|
|
#ifdef __STDC__
|
|
mpq_inv (MP_RAT *dest, const MP_RAT *src)
|
|
#else
|
|
mpq_inv (dest, src)
|
|
MP_RAT *dest;
|
|
const MP_RAT *src;
|
|
#endif
|
|
{
|
|
mp_size num_size = src->num.size;
|
|
mp_size den_size = src->den.size;
|
|
|
|
if (num_size == 0)
|
|
num_size = 1 / num_size; /* Divide by zero! */
|
|
|
|
if (num_size < 0)
|
|
{
|
|
num_size = -num_size;
|
|
den_size = -den_size;
|
|
}
|
|
dest->den.size = num_size;
|
|
dest->num.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 alloc = dest->num.alloc;
|
|
mp_ptr limb_ptr = dest->num.d;
|
|
|
|
dest->num.alloc = dest->den.alloc;
|
|
dest->num.d = dest->den.d;
|
|
|
|
dest->den.alloc = alloc;
|
|
dest->den.d = limb_ptr;
|
|
}
|
|
else
|
|
{
|
|
den_size = ABS (den_size);
|
|
if (dest->num.alloc < den_size)
|
|
_mpz_realloc (&(dest->num), den_size);
|
|
|
|
if (dest->den.alloc < num_size)
|
|
_mpz_realloc (&(dest->den), num_size);
|
|
|
|
MPN_COPY (dest->num.d, src->den.d, den_size);
|
|
MPN_COPY (dest->den.d, src->num.d, num_size);
|
|
}
|
|
}
|