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-rw-r--r--src/math/nextafter.c79
1 files changed, 79 insertions, 0 deletions
diff --git a/src/math/nextafter.c b/src/math/nextafter.c
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+/* origin: FreeBSD /usr/src/lib/msun/src/s_nextafter.c */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+/* IEEE functions
+ * nextafter(x,y)
+ * return the next machine floating-point number of x in the
+ * direction toward y.
+ * Special cases:
+ */
+
+#include "libm.h"
+
+double nextafter(double x, double y)
+{
+ volatile double t;
+ int32_t hx,hy,ix,iy;
+ uint32_t lx,ly;
+
+ EXTRACT_WORDS(hx, lx, x);
+ EXTRACT_WORDS(hy, ly, y);
+ ix = hx & 0x7fffffff; /* |x| */
+ iy = hy & 0x7fffffff; /* |y| */
+
+ if ((ix >= 0x7ff00000 && (ix-0x7ff00000)|lx) != 0 || /* x is nan */
+ (iy >= 0x7ff00000 && (iy-0x7ff00000)|ly) != 0) /* y is nan */
+ return x+y;
+ if (x == y) /* x == y */
+ return y;
+ if ((ix|lx) == 0) { /* x == 0 */
+ INSERT_WORDS(x, hy&0x80000000, 1); /* return +-minsubnormal */
+ /* raise underflow flag */
+ t = x*x;
+ if (t == x)
+ return t;
+ return x;
+ }
+ if (hx >= 0) { /* x > 0 */
+ if (hx > hy || (hx == hy && lx > ly)) { /* x > y, x -= ulp */
+ if (lx == 0)
+ hx--;
+ lx--;
+ } else { /* x < y, x += ulp */
+ lx++;
+ if (lx == 0)
+ hx++;
+ }
+ } else { /* x < 0 */
+ if (hy >= 0 || hx > hy || (hx == hy && lx > ly)) { /* x < y, x -= ulp */
+ if (lx == 0)
+ hx--;
+ lx--;
+ } else { /* x > y, x += ulp */
+ lx++;
+ if (lx == 0)
+ hx++;
+ }
+ }
+ hy = hx & 0x7ff00000;
+ if (hy >= 0x7ff00000) /* overflow */
+ return x+x;
+ if (hy < 0x00100000) { /* underflow */
+ /* raise underflow flag */
+ t = x*x;
+ if (t != x) {
+ INSERT_WORDS(y, hx, lx);
+ return y;
+ }
+ }
+ INSERT_WORDS(x, hx, lx);
+ return x;
+}