1/* mpq_add, mpq_sub -- add or subtract rational numbers.
2
3Copyright 1991, 1994, 1995, 1996, 1997, 2000, 2001, 2004, 2005 Free Software
4Foundation, Inc.
5
6This file is part of the GNU MP Library.
7
8The GNU MP Library is free software; you can redistribute it and/or modify
9it under the terms of the GNU Lesser General Public License as published by
10the Free Software Foundation; either version 3 of the License, or (at your
11option) any later version.
12
13The GNU MP Library is distributed in the hope that it will be useful, but
14WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
15or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
16License for more details.
17
18You should have received a copy of the GNU Lesser General Public License
19along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */
20
21#include "gmp.h"
22#include "gmp-impl.h"
23
24
25static void __gmpq_aors __GMP_PROTO ((REGPARM_3_1 (mpq_ptr, mpq_srcptr, mpq_srcptr, void (*) __GMP_PROTO ((mpz_ptr, mpz_srcptr, mpz_srcptr))))) REGPARM_ATTR (1);
26#define mpq_aors(w,x,y,fun)  __gmpq_aors (REGPARM_3_1 (w, x, y, fun))
27
28REGPARM_ATTR (1) static void
29mpq_aors (mpq_ptr rop, mpq_srcptr op1, mpq_srcptr op2,
30          void (*fun) __GMP_PROTO ((mpz_ptr, mpz_srcptr, mpz_srcptr)))
31{
32  mpz_t gcd;
33  mpz_t tmp1, tmp2;
34  mp_size_t op1_num_size = ABS (op1->_mp_num._mp_size);
35  mp_size_t op1_den_size =      op1->_mp_den._mp_size;
36  mp_size_t op2_num_size = ABS (op2->_mp_num._mp_size);
37  mp_size_t op2_den_size =      op2->_mp_den._mp_size;
38  TMP_DECL;
39
40  TMP_MARK;
41  MPZ_TMP_INIT (gcd, MIN (op1_den_size, op2_den_size));
42  MPZ_TMP_INIT (tmp1, op1_num_size + op2_den_size);
43  MPZ_TMP_INIT (tmp2, op2_num_size + op1_den_size);
44
45  /* ROP might be identical to either operand, so don't store the
46     result there until we are finished with the input operands.  We
47     dare to overwrite the numerator of ROP when we are finished
48     with the numerators of OP1 and OP2.  */
49
50  mpz_gcd (gcd, &(op1->_mp_den), &(op2->_mp_den));
51  if (! MPZ_EQUAL_1_P (gcd))
52    {
53      mpz_t t;
54
55      mpz_divexact_gcd (tmp1, &(op2->_mp_den), gcd);
56      mpz_mul (tmp1, &(op1->_mp_num), tmp1);
57
58      mpz_divexact_gcd (tmp2, &(op1->_mp_den), gcd);
59      mpz_mul (tmp2, &(op2->_mp_num), tmp2);
60
61      MPZ_TMP_INIT (t, MAX (ABS (tmp1->_mp_size), ABS (tmp2->_mp_size)) + 1);
62
63      (*fun) (t, tmp1, tmp2);
64      mpz_divexact_gcd (tmp2, &(op1->_mp_den), gcd);
65
66      mpz_gcd (gcd, t, gcd);
67      if (MPZ_EQUAL_1_P (gcd))
68        {
69          mpz_set (&(rop->_mp_num), t);
70          mpz_mul (&(rop->_mp_den), &(op2->_mp_den), tmp2);
71        }
72      else
73        {
74          mpz_divexact_gcd (&(rop->_mp_num), t, gcd);
75          mpz_divexact_gcd (tmp1, &(op2->_mp_den), gcd);
76          mpz_mul (&(rop->_mp_den), tmp1, tmp2);
77        }
78    }
79  else
80    {
81      /* The common divisor is 1.  This is the case (for random input) with
82	 probability 6/(pi**2), which is about 60.8%.  */
83      mpz_mul (tmp1, &(op1->_mp_num), &(op2->_mp_den));
84      mpz_mul (tmp2, &(op2->_mp_num), &(op1->_mp_den));
85      (*fun) (&(rop->_mp_num), tmp1, tmp2);
86      mpz_mul (&(rop->_mp_den), &(op1->_mp_den), &(op2->_mp_den));
87    }
88  TMP_FREE;
89}
90
91
92void
93mpq_add (mpq_ptr rop, mpq_srcptr op1, mpq_srcptr op2)
94{
95  mpq_aors (rop, op1, op2, mpz_add);
96}
97
98void
99mpq_sub (mpq_ptr rop, mpq_srcptr op1, mpq_srcptr op2)
100{
101  mpq_aors (rop, op1, op2, mpz_sub);
102}
103