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https://gitea.nishi.boats/pyrite-dev/milsko
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git-svn-id: http://svn2.nishi.boats/svn/milsko/trunk@557 b9cfdab3-6d41-4d17-bbe4-086880011989
77 lines
2.0 KiB
C
77 lines
2.0 KiB
C
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/* @(#)s_nextafter.c 1.3 95/01/18 */
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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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/* 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 "math.h"
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double nextafter(double x, double y) {
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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
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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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