86 lines
2.3 KiB
C
86 lines
2.3 KiB
C
|
/* mpq_sub -- subtract two rational numbers.
|
||
|
|
|
||
|
|
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_sub (MP_RAT *dif, const MP_RAT *min, const MP_RAT *sub)
|
||
|
|
#else
|
||
|
|
mpq_sub (dif, min, sub)
|
||
|
|
MP_RAT *dif;
|
||
|
|
const MP_RAT *min;
|
||
|
|
const MP_RAT *sub;
|
||
|
|
#endif
|
||
|
|
{
|
||
|
|
MP_INT gcd1, gcd2;
|
||
|
|
MP_INT tmp1, tmp2;
|
||
|
|
|
||
|
|
mpz_init (&gcd1);
|
||
|
|
mpz_init (&gcd2);
|
||
|
|
mpz_init (&tmp1);
|
||
|
|
mpz_init (&tmp2);
|
||
|
|
|
||
|
|
/* DIF might be identical to either operand, so don't store the
|
||
|
|
result there until we are finished with the input operands. We
|
||
|
|
dare to overwrite the numerator of DIF when we are finished
|
||
|
|
with the numerators of MIN and SUB. */
|
||
|
|
|
||
|
|
mpz_gcd (&gcd1, &(min->den), &(sub->den));
|
||
|
|
if (gcd1.size > 1 || gcd1.d[0] != 1)
|
||
|
|
{
|
||
|
|
MP_INT t;
|
||
|
|
|
||
|
|
mpz_init (&t);
|
||
|
|
|
||
|
|
mpz_div (&tmp1, &(sub->den), &gcd1);
|
||
|
|
mpz_mul (&tmp1, &(min->num), &tmp1);
|
||
|
|
|
||
|
|
mpz_div (&tmp2, &(min->den), &gcd1);
|
||
|
|
mpz_mul (&tmp2, &(sub->num), &tmp2);
|
||
|
|
|
||
|
|
mpz_sub (&t, &tmp1, &tmp2);
|
||
|
|
mpz_gcd (&gcd2, &t, &gcd1);
|
||
|
|
|
||
|
|
mpz_div (&(dif->num), &t, &gcd2);
|
||
|
|
|
||
|
|
mpz_div (&tmp1, &(min->den), &gcd1);
|
||
|
|
mpz_div (&tmp2, &(sub->den), &gcd2);
|
||
|
|
mpz_mul (&(dif->den), &tmp1, &tmp2);
|
||
|
|
|
||
|
|
mpz_clear (&t);
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
/* The common divisior is 1. This is the case (for random input) with
|
||
|
|
probability 6/(pi**2). */
|
||
|
|
mpz_mul (&tmp1, &(min->num), &(sub->den));
|
||
|
|
mpz_mul (&tmp2, &(sub->num), &(min->den));
|
||
|
|
mpz_sub (&(dif->num), &tmp1, &tmp2);
|
||
|
|
mpz_mul (&(dif->den), &(min->den), &(sub->den));
|
||
|
|
}
|
||
|
|
|
||
|
|
mpz_clear (&tmp2);
|
||
|
|
mpz_clear (&tmp1);
|
||
|
|
mpz_clear (&gcd2);
|
||
|
|
mpz_clear (&gcd1);
|
||
|
|
}
|