1  /* Return the least floating-point number greater than X.
       2     Copyright (C) 2016-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       4  
       5     The GNU C Library is free software; you can redistribute it and/or
       6     modify it under the terms of the GNU Lesser General Public
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the License, or (at your option) any later version.
       9  
      10     The GNU C Library is distributed in the hope that it will be useful,
      11     but WITHOUT ANY WARRANTY; without even the implied warranty of
      12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      13     Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public
      16     License along with the GNU C Library; if not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #include <float.h>
      20  #include <math.h>
      21  #include <math_private.h>
      22  #include <libm-alias-double.h>
      23  
      24  /* Return the least floating-point number greater than X.  */
      25  double
      26  __nextup (double x)
      27  {
      28    int32_t hx, ix;
      29    uint32_t lx;
      30  
      31    EXTRACT_WORDS (hx, lx, x);
      32    ix = hx & 0x7fffffff;
      33  
      34    if (((ix >= 0x7ff00000) && ((ix - 0x7ff00000) | lx) != 0))  /* x is nan.  */
      35      return x + x;
      36    if ((ix | lx) == 0)
      37      return DBL_TRUE_MIN;
      38    if (hx >= 0)
      39      {				/* x > 0.  */
      40        if (isinf (x))
      41          return x;
      42        lx += 1;
      43        if (lx == 0)
      44          hx += 1;
      45      }
      46    else
      47      {				/* x < 0.  */
      48        if (lx == 0)
      49          hx -= 1;
      50        lx -= 1;
      51      }
      52    INSERT_WORDS (x, hx, lx);
      53    return x;
      54  }
      55  
      56  libm_alias_double (__nextup, nextup)