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Annotation of 43BSDReno/lib/libm/common_source/floor.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1985 Regents of the University of California.
        !             3:  * All rights reserved.
        !             4:  *
        !             5:  * Redistribution and use in source and binary forms are permitted
        !             6:  * provided that: (1) source distributions retain this entire copyright
        !             7:  * notice and comment, and (2) distributions including binaries display
        !             8:  * the following acknowledgement:  ``This product includes software
        !             9:  * developed by the University of California, Berkeley and its contributors''
        !            10:  * in the documentation or other materials provided with the distribution
        !            11:  * and in all advertising materials mentioning features or use of this
        !            12:  * software. Neither the name of the University nor the names of its
        !            13:  * contributors may be used to endorse or promote products derived
        !            14:  * from this software without specific prior written permission.
        !            15:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
        !            16:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
        !            17:  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            18:  *
        !            19:  * All recipients should regard themselves as participants in an ongoing
        !            20:  * research project and hence should feel obligated to report their
        !            21:  * experiences (good or bad) with these elementary function codes, using
        !            22:  * the sendbug(8) program, to the authors.
        !            23:  */
        !            24: 
        !            25: #ifndef lint
        !            26: static char sccsid[] = "@(#)floor.c    5.6 (Berkeley) 6/1/90";
        !            27: #endif /* not lint */
        !            28: 
        !            29: #include "mathimpl.h"
        !            30: 
        !            31: vc(L, 4503599627370496.0E0 ,0000,5c00,0000,0000, 55, 1.0) /* 2**55 */
        !            32: 
        !            33: ic(L, 4503599627370496.0E0, 52, 1.0)                     /* 2**52 */
        !            34: 
        !            35: #ifdef vccast
        !            36: #define        L       vccast(L)
        !            37: #endif
        !            38: 
        !            39: 
        !            40: double ceil();
        !            41: double floor();
        !            42: 
        !            43: /*
        !            44:  * floor(x) := the largest integer no larger than x;
        !            45:  * ceil(x) := -floor(-x), for all real x.
        !            46:  *
        !            47:  * Note: Inexact will be signaled if x is not an integer, as is
        !            48:  *     customary for IEEE 754.  No other signal can be emitted.
        !            49:  */
        !            50: double
        !            51: floor(x)
        !            52: double x;
        !            53: {
        !            54:        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 -ceil(-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: double
        !            72: ceil(x)
        !            73: double x;
        !            74: {
        !            75:        double y;
        !            76: 
        !            77:        if (
        !            78: #if !defined(vax)&&!defined(tahoe)
        !            79:                x != x ||       /* NaN */
        !            80: #endif /* !defined(vax)&&!defined(tahoe) */
        !            81:                x >= L)         /* already an even integer */
        !            82:                return x;
        !            83:        else if (x < (double)0)
        !            84:                return -floor(-x);
        !            85:        else {                  /* now 0 <= x < L */
        !            86:                y = L+x;                /* destructive store must be forced */
        !            87:                y -= L;                 /* an integer, and |x-y| < 1 */
        !            88:                return x > y ? y+(double)1 : y;
        !            89:        }
        !            90: }
        !            91: 
        !            92: #ifndef national                       /* rint() is in ./NATIONAL/support.s */
        !            93: /*
        !            94:  * algorithm for rint(x) in pseudo-pascal form ...
        !            95:  *
        !            96:  * real rint(x): real x;
        !            97:  *     ... delivers integer nearest x in direction of prevailing rounding
        !            98:  *     ... mode
        !            99:  * const       L = (last consecutive integer)/2
        !           100:  *       = 2**55; for VAX D
        !           101:  *       = 2**52; for IEEE 754 Double
        !           102:  * real        s,t;
        !           103:  * begin
        !           104:  *     if x != x then return x;                ... NaN
        !           105:  *     if |x| >= L then return x;              ... already an integer
        !           106:  *     s := copysign(L,x);
        !           107:  *     t := x + s;                             ... = (x+s) rounded to integer
        !           108:  *     return t - s
        !           109:  * end;
        !           110:  *
        !           111:  * Note: Inexact will be signaled if x is not an integer, as is
        !           112:  *     customary for IEEE 754.  No other signal can be emitted.
        !           113:  */
        !           114: double
        !           115: rint(x)
        !           116: double x;
        !           117: {
        !           118:        double s,t;
        !           119:        const double one = 1.0;
        !           120: 
        !           121: #if !defined(vax)&&!defined(tahoe)
        !           122:        if (x != x)                             /* NaN */
        !           123:                return (x);
        !           124: #endif /* !defined(vax)&&!defined(tahoe) */
        !           125:        if (copysign(x,one) >= L)               /* already an integer */
        !           126:            return (x);
        !           127:        s = copysign(L,x);
        !           128:        t = x + s;                              /* x+s rounded to integer */
        !           129:        return (t - s);
        !           130: }
        !           131: #endif /* not national */

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