86 lines
2.3 KiB
C
86 lines
2.3 KiB
C
/* mpq_add -- add two rational numbers.
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Copyright (C) 1991 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 General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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The GNU MP Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with the GNU MP Library; see the file COPYING. If not, write to
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the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, 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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#ifdef __STDC__
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mpq_add (MP_RAT *sum, const MP_RAT *a1, const MP_RAT *a2)
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#else
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mpq_add (sum, a1, a2)
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MP_RAT *sum;
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const MP_RAT *a1;
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const MP_RAT *a2;
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#endif
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{
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MP_INT gcd1, gcd2;
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MP_INT tmp1, tmp2;
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mpz_init (&gcd1);
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mpz_init (&gcd2);
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mpz_init (&tmp1);
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mpz_init (&tmp2);
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/* SUM might be identical to either operand, so don't store the
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result there until we are finished with the input operands. We
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dare to overwrite the numerator of SUM when we are finished
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with the numerators of A1 and A2. */
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mpz_gcd (&gcd1, &(a1->den), &(a2->den));
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if (gcd1.size > 1 || gcd1.d[0] != 1)
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{
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MP_INT t;
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mpz_init (&t);
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mpz_div (&tmp1, &(a2->den), &gcd1);
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mpz_mul (&tmp1, &(a1->num), &tmp1);
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mpz_div (&tmp2, &(a1->den), &gcd1);
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mpz_mul (&tmp2, &(a2->num), &tmp2);
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mpz_add (&t, &tmp1, &tmp2);
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mpz_gcd (&gcd2, &t, &gcd1);
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mpz_div (&(sum->num), &t, &gcd2);
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mpz_div (&tmp1, &(a1->den), &gcd1);
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mpz_div (&tmp2, &(a2->den), &gcd2);
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mpz_mul (&(sum->den), &tmp1, &tmp2);
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mpz_clear (&t);
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}
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else
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{
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/* The common divisior is 1. This is the case (for random input) with
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probability 6/(pi**2). */
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mpz_mul (&tmp1, &(a1->num), &(a2->den));
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mpz_mul (&tmp2, &(a2->num), &(a1->den));
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mpz_add (&(sum->num), &tmp1, &tmp2);
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mpz_mul (&(sum->den), &(a1->den), &(a2->den));
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}
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mpz_clear (&tmp2);
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mpz_clear (&tmp1);
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mpz_clear (&gcd2);
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mpz_clear (&gcd1);
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}
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