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113 lines
3.6 KiB
C
113 lines
3.6 KiB
C
/* @(#)s_nextafter.c 1.3 95/01/18 */
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/*
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* Copyright (c) 2015-2017 Carsten Sonne Larsen <cs@innolan.dk>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* The origin source code can be obtained from:
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* http://www.netlib.org/fdlibm/s_nextafter.c
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*
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*/
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunSoft, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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// NOTICE: Not a part of libamath yet
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/* IEEE functions
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* nextafter(x,y)
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* return the next machine floating-point number of x in the
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* direction toward y.
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* Special cases:
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*/
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#include "fdlibm.h"
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#ifdef __STDC__
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double nextafter(double x, double y)
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#else
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double nextafter(x,y)
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double x,y;
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#endif
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{
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int hx,hy,ix,iy;
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unsigned lx,ly;
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hx = __HI(x); /* high word of x */
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lx = __LO(x); /* low word of x */
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hy = __HI(y); /* high word of y */
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ly = __LO(y); /* low word of y */
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ix = hx&0x7fffffff; /* |x| */
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iy = hy&0x7fffffff; /* |y| */
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if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */
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((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */
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return x+y;
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if(x==y) return x; /* x=y, return x */
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if((ix|lx)==0) { /* x == 0 */
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__HI(x) = hy&0x80000000; /* return +-minsubnormal */
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__LO(x) = 1;
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y = x*x;
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if(y==x) return y;
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else return x; /* raise underflow flag */
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}
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if(hx>=0) { /* x > 0 */
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if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */
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if(lx==0) hx -= 1;
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lx -= 1;
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} else { /* x < y, x += ulp */
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lx += 1;
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if(lx==0) hx += 1;
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}
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} else { /* x < 0 */
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if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))) { /* x < y, x -= ulp */
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if(lx==0) hx -= 1;
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lx -= 1;
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} else { /* x > y, x += ulp */
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lx += 1;
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if(lx==0) hx += 1;
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}
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}
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hy = hx&0x7ff00000;
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if(hy>=0x7ff00000) return x+x; /* overflow */
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if(hy<0x00100000) { /* underflow */
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y = x*x;
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if(y!=x) { /* raise underflow flag */
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__HI(y) = hx;
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__LO(y) = lx;
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return y;
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}
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}
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__HI(x) = hx;
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__LO(x) = lx;
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return x;
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}
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