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Annotation of OpenXM_contrib/gmp/mpfr/div_2ui.c, Revision 1.1

1.1     ! ohara       1: /* mpfr_div_2ui -- divide a floating-point number by a power of two
        !             2:
        !             3: Copyright 1999, 2001 Free Software Foundation, Inc.
        !             4:
        !             5: This file is part of the MPFR Library.
        !             6:
        !             7: The MPFR Library is free software; you can redistribute it and/or modify
        !             8: it under the terms of the GNU Lesser General Public License as published by
        !             9: the Free Software Foundation; either version 2.1 of the License, or (at your
        !            10: option) any later version.
        !            11:
        !            12: The MPFR 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 Lesser General Public
        !            15: License for more details.
        !            16:
        !            17: You should have received a copy of the GNU Lesser General Public License
        !            18: along with the MPFR 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: #include "mpfr.h"
        !            25: #include "mpfr-impl.h"
        !            26:
        !            27: int
        !            28: mpfr_div_2ui (mpfr_ptr y, mpfr_srcptr x, unsigned long int n, mp_rnd_t rnd_mode)
        !            29: {
        !            30:   int inexact;
        !            31:
        !            32:   inexact = y != x ? mpfr_set (y, x, rnd_mode) : 0;
        !            33:
        !            34:   if (MPFR_IS_FP(y) && MPFR_NOTZERO(y))
        !            35:     {
        !            36:       /* n will have to be casted to long to make sure that the addition
        !            37:          and subtraction below (for overflow detection) are signed */
        !            38:       while (n > LONG_MAX)
        !            39:         {
        !            40:           int inex2;
        !            41:
        !            42:           n -= LONG_MAX;
        !            43:           inex2 = mpfr_div_2ui(y, y, LONG_MAX, rnd_mode);
        !            44:           if (inex2)
        !            45:             return inex2; /* underflow */
        !            46:         }
        !            47:
        !            48:       /* MPFR_EMAX_MAX - (long) n is signed and doesn't lead to an overflow;
        !            49:          the first test useful so that the real test can't lead to an
        !            50:          overflow. */
        !            51:       if (__mpfr_emin > MPFR_EMAX_MAX - (long) n ||
        !            52:           MPFR_EXP(y) < __mpfr_emin + (long) n)
        !            53:         return mpfr_set_underflow (y, rnd_mode, MPFR_SIGN(y));
        !            54:
        !            55:       MPFR_EXP(y) -= (long) n;
        !            56:     }
        !            57:
        !            58:   return inexact;
        !            59: }