1 /* 2 * Copyright (c) 1985, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * %sccs.include.redist.c% 6 */ 7 8 #ifndef lint 9 static char sccsid[] = "@(#)floor.c 8.1 (Berkeley) 06/04/93"; 10 #endif /* not lint */ 11 12 #include "mathimpl.h" 13 14 vc(L, 4503599627370496.0E0 ,0000,5c00,0000,0000, 55, 1.0) /* 2**55 */ 15 16 ic(L, 4503599627370496.0E0, 52, 1.0) /* 2**52 */ 17 18 #ifdef vccast 19 #define L vccast(L) 20 #endif 21 22 /* 23 * floor(x) := the largest integer no larger than x; 24 * ceil(x) := -floor(-x), for all real x. 25 * 26 * Note: Inexact will be signaled if x is not an integer, as is 27 * customary for IEEE 754. No other signal can be emitted. 28 */ 29 double 30 floor(x) 31 double x; 32 { 33 volatile double y; 34 35 if ( 36 #if !defined(vax)&&!defined(tahoe) 37 x != x || /* NaN */ 38 #endif /* !defined(vax)&&!defined(tahoe) */ 39 x >= L) /* already an even integer */ 40 return x; 41 else if (x < (double)0) 42 return -ceil(-x); 43 else { /* now 0 <= x < L */ 44 y = L+x; /* destructive store must be forced */ 45 y -= L; /* an integer, and |x-y| < 1 */ 46 return x < y ? y-(double)1 : y; 47 } 48 } 49 50 double 51 ceil(x) 52 double x; 53 { 54 volatile double y; 55 56 if ( 57 #if !defined(vax)&&!defined(tahoe) 58 x != x || /* NaN */ 59 #endif /* !defined(vax)&&!defined(tahoe) */ 60 x >= L) /* already an even integer */ 61 return x; 62 else if (x < (double)0) 63 return -floor(-x); 64 else { /* now 0 <= x < L */ 65 y = L+x; /* destructive store must be forced */ 66 y -= L; /* an integer, and |x-y| < 1 */ 67 return x > y ? y+(double)1 : y; 68 } 69 } 70 71 #ifndef ns32000 /* rint() is in ./NATIONAL/support.s */ 72 /* 73 * algorithm for rint(x) in pseudo-pascal form ... 74 * 75 * real rint(x): real x; 76 * ... delivers integer nearest x in direction of prevailing rounding 77 * ... mode 78 * const L = (last consecutive integer)/2 79 * = 2**55; for VAX D 80 * = 2**52; for IEEE 754 Double 81 * real s,t; 82 * begin 83 * if x != x then return x; ... NaN 84 * if |x| >= L then return x; ... already an integer 85 * s := copysign(L,x); 86 * t := x + s; ... = (x+s) rounded to integer 87 * return t - s 88 * end; 89 * 90 * Note: Inexact will be signaled if x is not an integer, as is 91 * customary for IEEE 754. No other signal can be emitted. 92 */ 93 double 94 rint(x) 95 double x; 96 { 97 double s; 98 volatile double t; 99 const double one = 1.0; 100 101 #if !defined(vax)&&!defined(tahoe) 102 if (x != x) /* NaN */ 103 return (x); 104 #endif /* !defined(vax)&&!defined(tahoe) */ 105 if (copysign(x,one) >= L) /* already an integer */ 106 return (x); 107 s = copysign(L,x); 108 t = x + s; /* x+s rounded to integer */ 109 return (t - s); 110 } 111 #endif /* not national */ 112