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Annotation of OpenXM_contrib/gmp/mpfr/sub_ui.c, Revision 1.1.1.1

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: }