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