summaryrefslogtreecommitdiff
path: root/src/math/s_nextafter.c
diff options
context:
space:
mode:
Diffstat (limited to 'src/math/s_nextafter.c')
-rw-r--r--src/math/s_nextafter.c72
1 files changed, 72 insertions, 0 deletions
diff --git a/src/math/s_nextafter.c b/src/math/s_nextafter.c
new file mode 100644
index 00000000..46d298ec
--- /dev/null
+++ b/src/math/s_nextafter.c
@@ -0,0 +1,72 @@
+/* @(#)s_nextafter.c 5.1 93/09/24 */
+/*
+ * ====================================================
+ * 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 <math.h>
+#include "math_private.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) return y; /* x=y, return y */
+ if((ix|lx)==0) { /* x == 0 */
+ INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */
+ t = x*x;
+ if(t==x) return t; else return x; /* raise underflow flag */
+ }
+ if(hx>=0) { /* x > 0 */
+ if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */
+ if(lx==0) hx -= 1;
+ lx -= 1;
+ } else { /* x < y, x += ulp */
+ lx += 1;
+ if(lx==0) hx += 1;
+ }
+ } else { /* x < 0 */
+ if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */
+ if(lx==0) hx -= 1;
+ lx -= 1;
+ } else { /* x > y, x += ulp */
+ lx += 1;
+ if(lx==0) hx += 1;
+ }
+ }
+ hy = hx&0x7ff00000;
+ if(hy>=0x7ff00000) return x+x; /* overflow */
+ if(hy<0x00100000) { /* underflow */
+ t = x*x;
+ if(t!=x) { /* raise underflow flag */
+ INSERT_WORDS(y,hx,lx);
+ return y;
+ }
+ }
+ INSERT_WORDS(x,hx,lx);
+ return x;
+}