BSD 4_4 release

[unix-history] / usr / src / lib / libm / common_source / floor.c

/*
* Copyright (c) 1985, 1993
*      The Regents of the University of California.  All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
*    must display the following acknowledgement:
*      This product includes software developed by the University of
*      California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
*    may be used to endorse or promote products derived from this software
*    without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/

#ifndef lint
static char sccsid[] = "@(#)floor.c     8.1 (Berkeley) 6/4/93";
#endif /* not lint */

#include "mathimpl.h"

vc(L, 4503599627370496.0E0 ,0000,5c00,0000,0000, 55, 1.0) /* 2**55 */

ic(L, 4503599627370496.0E0, 52, 1.0)                      /* 2**52 */

#ifdef vccast
#define L       vccast(L)
#endif

/*
* floor(x) := the largest integer no larger than x;
* ceil(x) := -floor(-x), for all real x.
*
* Note: Inexact will be signaled if x is not an integer, as is
*      customary for IEEE 754.  No other signal can be emitted.
*/
double
floor(x)
double x;
{
       volatile double y;

       if (
#if !defined(vax)&&!defined(tahoe)
               x != x ||       /* NaN */
#endif  /* !defined(vax)&&!defined(tahoe) */
               x >= L)         /* already an even integer */
               return x;
       else if (x < (double)0)
               return -ceil(-x);
       else {                  /* now 0 <= x < L */
               y = L+x;                /* destructive store must be forced */
               y -= L;                 /* an integer, and |x-y| < 1 */
               return x < y ? y-(double)1 : y;
       }
}

double
ceil(x)
double x;
{
       volatile double y;

       if (
#if !defined(vax)&&!defined(tahoe)
               x != x ||       /* NaN */
#endif  /* !defined(vax)&&!defined(tahoe) */
               x >= L)         /* already an even integer */
               return x;
       else if (x < (double)0)
               return -floor(-x);
       else {                  /* now 0 <= x < L */
               y = L+x;                /* destructive store must be forced */
               y -= L;                 /* an integer, and |x-y| < 1 */
               return x > y ? y+(double)1 : y;
       }
}

#ifndef ns32000                 /* rint() is in ./NATIONAL/support.s */
/*
* algorithm for rint(x) in pseudo-pascal form ...
*
* real rint(x): real x;
*      ... delivers integer nearest x in direction of prevailing rounding
*      ... mode
* const        L = (last consecutive integer)/2
*        = 2**55; for VAX D
*        = 2**52; for IEEE 754 Double
* real s,t;
* begin
*      if x != x then return x;                ... NaN
*      if |x| >= L then return x;              ... already an integer
*      s := copysign(L,x);
*      t := x + s;                             ... = (x+s) rounded to integer
*      return t - s
* end;
*
* Note: Inexact will be signaled if x is not an integer, as is
*      customary for IEEE 754.  No other signal can be emitted.
*/
double
rint(x)
double x;
{
       double s;
       volatile double t;
       const double one = 1.0;

#if !defined(vax)&&!defined(tahoe)
       if (x != x)                             /* NaN */
               return (x);
#endif  /* !defined(vax)&&!defined(tahoe) */
       if (copysign(x,one) >= L)               /* already an integer */
           return (x);
       s = copysign(L,x);
       t = x + s;                              /* x+s rounded to integer */
       return (t - s);
}
#endif  /* not national */