sysdeps/generic/floor.c

   1 /* snarfed from BSD common_source/floor.c:
   2  * Copyright (c) 1985 Regents of the University of California.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 #ifndef lint
  35 static char sccsid[] = "@(#)floor.c     5.7 (Berkeley) 10/9/90";
  36 #endif /* not lint */
  37
  38 #include "mathimpl.h"
  39
  40 vc(L, 4503599627370496.0E0 ,0000,5c00,0000,0000, 55, 1.0) /* 2**55 */
  41
  42 ic(L, 4503599627370496.0E0, 52, 1.0)                      /* 2**52 */
  43
  44 #ifdef vccast
  45 #define L       vccast(L)
  46 #endif
  47
  48 /*
  49  * floor(x) := the largest integer no larger than x;
  50  * ceil(x) := -floor(-x), for all real x.
  51  *
  52  * Note: Inexact will be signaled if x is not an integer, as is
  53  *      customary for IEEE 754.  No other signal can be emitted.
  54  */
  55 double
  56 floor(x)
  57 double x;
  58 {
  59         double y;
  60
  61         if (
  62 #if !defined(vax)&&!defined(tahoe)
  63                 x != x ||       /* NaN */
  64 #endif  /* !defined(vax)&&!defined(tahoe) */
  65                 x >= L)         /* already an even integer */
  66                 return x;
  67         else if (x < (double)0)
  68                 return -ceil(-x);
  69         else {                  /* now 0 <= x < L */
  70                 y = L+x;                /* destructive store must be forced */
  71                 y -= L;                 /* an integer, and |x-y| < 1 */
  72                 return x < y ? y-(double)1 : y;
  73         }
  74 }