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n_floor.c revision 1.5 
      1 /*      $NetBSD: n_floor.c,v 1.5 2003/08/07 16:44:51 agc Exp $ */
      2 /*
      3  * Copyright (c) 1985, 1993
      4  *	The Regents of the University of California.  All rights reserved.
      5  *
      6  * Redistribution and use in source and binary forms, with or without
      7  * modification, are permitted provided that the following conditions
      8  * are met:
      9  * 1. Redistributions of source code must retain the above copyright
     10  *    notice, this list of conditions and the following disclaimer.
     11  * 2. Redistributions in binary form must reproduce the above copyright
     12  *    notice, this list of conditions and the following disclaimer in the
     13  *    documentation and/or other materials provided with the distribution.
     14  * 3. Neither the name of the University nor the names of its contributors
     15  *    may be used to endorse or promote products derived from this software
     16  *    without specific prior written permission.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     21  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     28  * SUCH DAMAGE.
     29  */
     30 
     31 #ifndef lint
     32 #if 0
     33 static char sccsid[] = "@(#)floor.c	8.1 (Berkeley) 6/4/93";
     34 #endif
     35 #endif /* not lint */
     36 
     37 #define _LIBM_STATIC
     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(double x)
     57 {
     58 	volatile double y;
     59 
     60 	if (
     61 #if !defined(__vax__)&&!defined(tahoe)
     62 		x != x ||	/* NaN */
     63 #endif	/* !defined(__vax__)&&!defined(tahoe) */
     64 		x >= L)		/* already an even integer */
     65 		return x;
     66 	else if (x < (double)0)
     67 		return -ceil(-x);
     68 	else {			/* now 0 <= x < L */
     69 		y = L+x;		/* destructive store must be forced */
     70 		y -= L;			/* an integer, and |x-y| < 1 */
     71 		return x < y ? y-(double)1 : y;
     72 	}
     73 }
     74 
     75 double
     76 ceil(double x)
     77 {
     78 	volatile double y;
     79 
     80 	if (
     81 #if !defined(__vax__)&&!defined(tahoe)
     82 		x != x ||	/* NaN */
     83 #endif	/* !defined(__vax__)&&!defined(tahoe) */
     84 		x >= L)		/* already an even integer */
     85 		return x;
     86 	else if (x < (double)0)
     87 		return -floor(-x);
     88 	else {			/* now 0 <= x < L */
     89 		y = L+x;		/* destructive store must be forced */
     90 		y -= L;			/* an integer, and |x-y| < 1 */
     91 		return x > y ? y+(double)1 : y;
     92 	}
     93 }
     94 
     95 #ifndef ns32000			/* rint() is in ./NATIONAL/support.s */
     96 /*
     97  * algorithm for rint(x) in pseudo-pascal form ...
     98  *
     99  * real rint(x): real x;
    100  *	... delivers integer nearest x in direction of prevailing rounding
    101  *	... mode
    102  * const	L = (last consecutive integer)/2
    103  * 	  = 2**55; for VAX D
    104  * 	  = 2**52; for IEEE 754 Double
    105  * real	s,t;
    106  * begin
    107  * 	if x != x then return x;		... NaN
    108  * 	if |x| >= L then return x;		... already an integer
    109  * 	s := copysign(L,x);
    110  * 	t := x + s;				... = (x+s) rounded to integer
    111  * 	return t - s
    112  * end;
    113  *
    114  * Note: Inexact will be signaled if x is not an integer, as is
    115  *	customary for IEEE 754.  No other signal can be emitted.
    116  */
    117 double
    118 rint(double x)
    119 {
    120 	double s;
    121 	volatile double t;
    122 	const double one = 1.0;
    123 
    124 #if !defined(__vax__)&&!defined(tahoe)
    125 	if (x != x)				/* NaN */
    126 		return (x);
    127 #endif	/* !defined(__vax__)&&!defined(tahoe) */
    128 	if (copysign(x,one) >= L)		/* already an integer */
    129 	    return (x);
    130 	s = copysign(L,x);
    131 	t = x + s;				/* x+s rounded to integer */
    132 	return (t - s);
    133 }
    134 #endif	/* not national */
    135