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

1.1     ! ohara       1: /* mpfr_sub_ui -- subtract a floating-point number and a machine integer
        !             2:
        !             3: Copyright 2000, 2001, 2002 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 "longlong.h"
        !            25: #include "mpfr.h"
        !            26: #include "mpfr-impl.h"
        !            27:
        !            28: int
        !            29: mpfr_sub_ui (mpfr_ptr y, mpfr_srcptr x, unsigned long int u, mp_rnd_t rnd_mode)
        !            30: {
        !            31:   if (u)  /* if u=0, do nothing */
        !            32:   {
        !            33:     mpfr_t uu;
        !            34:     mp_limb_t up[1];
        !            35:     unsigned long cnt;
        !            36:     int inex;
        !            37:
        !            38:     MPFR_INIT1(up, uu, BITS_PER_MP_LIMB, 1);
        !            39:     count_leading_zeros(cnt, (mp_limb_t) u);
        !            40:     *up = (mp_limb_t) u << cnt;
        !            41:     MPFR_EXP(uu) = BITS_PER_MP_LIMB - cnt;
        !            42:
        !            43:     /* Optimization note: Exponent operations may be removed
        !            44:        if mpfr_sub works even when uu is out-of-range. */
        !            45:     mpfr_save_emin_emax();
        !            46:     inex = mpfr_sub(y, x, uu, rnd_mode);
        !            47:     MPFR_RESTORE_RET(inex, y, rnd_mode);
        !            48:   }
        !            49:   else
        !            50:     return mpfr_set (y, x, rnd_mode);
        !            51: }