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Annotation of OpenXM/src/kan96xx/gmp-2.0.2-ssh-2/mpq/sub.c, Revision 1.1

1.1     ! takayama    1: /* mpq_sub -- subtract two rational numbers.
        !             2:
        !             3: Copyright (C) 1991, 1994, 1995, 1996 Free Software Foundation, Inc.
        !             4:
        !             5: This file is part of the GNU MP Library.
        !             6:
        !             7: The GNU MP Library is free software; you can redistribute it and/or modify
        !             8: it under the terms of the GNU Library General Public License as published by
        !             9: the Free Software Foundation; either version 2 of the License, or (at your
        !            10: option) any later version.
        !            11:
        !            12: The GNU MP Library is distributed in the hope that it will be useful, but
        !            13: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
        !            14: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
        !            15: License for more details.
        !            16:
        !            17: You should have received a copy of the GNU Library General Public License
        !            18: along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
        !            19: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
        !            20: MA 02111-1307, USA. */
        !            21:
        !            22: #include "gmp.h"
        !            23: #include "gmp-impl.h"
        !            24:
        !            25: void
        !            26: #if __STDC__
        !            27: mpq_sub (mpq_ptr rop, mpq_srcptr op1, mpq_srcptr op2)
        !            28: #else
        !            29: mpq_sub (rop, op1, op2)
        !            30:      mpq_ptr rop;
        !            31:      mpq_srcptr op1;
        !            32:      mpq_srcptr op2;
        !            33: #endif
        !            34: {
        !            35:   mpz_t gcd;
        !            36:   mpz_t tmp1, tmp2;
        !            37:   mp_size_t op1_num_size = ABS (op1->_mp_num._mp_size);
        !            38:   mp_size_t op1_den_size = ABS (op1->_mp_den._mp_size);
        !            39:   mp_size_t op2_num_size = ABS (op2->_mp_num._mp_size);
        !            40:   mp_size_t op2_den_size = ABS (op2->_mp_den._mp_size);
        !            41:   TMP_DECL (marker);
        !            42:
        !            43:   TMP_MARK (marker);
        !            44:   MPZ_TMP_INIT (gcd, MIN (op1_den_size, op2_den_size));
        !            45:   MPZ_TMP_INIT (tmp1, op1_num_size + op2_den_size);
        !            46:   MPZ_TMP_INIT (tmp2, op2_num_size + op1_den_size);
        !            47:
        !            48:   /* ROP might be identical to either operand, so don't store the
        !            49:      result there until we are finished with the input operands.  We
        !            50:      dare to overwrite the numerator of ROP when we are finished
        !            51:      with the numerators of OP1 and OP2.  */
        !            52:
        !            53:   mpz_gcd (gcd, &(op1->_mp_den), &(op2->_mp_den));
        !            54:   if (gcd->_mp_size > 1 || gcd->_mp_d[0] != 1)
        !            55:     {
        !            56:       mpz_t t;
        !            57:
        !            58:       mpz_divexact (tmp1, &(op2->_mp_den), gcd);
        !            59:       mpz_mul (tmp1, &(op1->_mp_num), tmp1);
        !            60:
        !            61:       mpz_divexact (tmp2, &(op1->_mp_den), gcd);
        !            62:       mpz_mul (tmp2, &(op2->_mp_num), tmp2);
        !            63:
        !            64:       MPZ_TMP_INIT (t, MAX (ABS (tmp1->_mp_size), ABS (tmp2->_mp_size)) + 1);
        !            65:
        !            66:       mpz_sub (t, tmp1, tmp2);
        !            67:       mpz_divexact (tmp1, &(op1->_mp_den), gcd);
        !            68:       mpz_gcd (gcd, t, gcd);
        !            69:
        !            70:       mpz_divexact (&(rop->_mp_num), t, gcd);
        !            71:
        !            72:       mpz_divexact (tmp2, &(op2->_mp_den), gcd);
        !            73:       mpz_mul (&(rop->_mp_den), tmp1, tmp2);
        !            74:     }
        !            75:   else
        !            76:     {
        !            77:       /* The common divisor is 1.  This is the case (for random input) with
        !            78:         probability 6/(pi**2).  */
        !            79:       mpz_mul (tmp1, &(op1->_mp_num), &(op2->_mp_den));
        !            80:       mpz_mul (tmp2, &(op2->_mp_num), &(op1->_mp_den));
        !            81:       mpz_sub (&(rop->_mp_num), tmp1, tmp2);
        !            82:       mpz_mul (&(rop->_mp_den), &(op1->_mp_den), &(op2->_mp_den));
        !            83:     }
        !            84:   TMP_FREE (marker);
        !            85: }