date and time created 85/09/06 17:52:50 by zliu

SCCS-vsn: lib/libm/common_source/floor.c 1.1

diff --git a/usr/src/lib/libm/common_source/floor.c b/usr/src/lib/libm/common_source/floor.c
new file mode 100644 (file)
index 0000000..ffd850a
--- /dev/null
+++ b/usr/src/lib/libm/common_source/floor.c
@@ -0,0 +1,75 @@
+/* @(#)floor.c 1.1 (ELEFUNT) %G% */
+
+/*
+ * floor and ceil-- greatest integer <= arg
+ * (resp least >=)
+ */
+
+double modf();
+
+double
+floor(d)
+double d;
+{
+       double fract;
+
+       if (d<0.0) {
+               d = -d;
+               fract = modf(d, &d);
+               if (fract != 0.0)
+                       d += 1;
+               d = -d;
+       } else
+               modf(d, &d);
+       return(d);
+}
+
+double
+ceil(d)
+double d;
+{
+       return(-floor(-d));
+}
+
+/*
+ * algorithm for rint(x) in pseudo-pascal form ...
+ *
+ * real rint(x): real x;
+ *     ... delivers integer nearest x in direction of prevailing rounding
+ *     ... mode
+ * const       L = (last consecutive integer)/2
+ *       = 2**55; for VAX D
+ *       = 2**52; for IEEE 754 Double
+ * real        s,t;
+ * begin
+ *     if x != x then return x;                ... NaN
+ *     if |x| >= L then return x;              ... already an integer
+ *     s := copysign(L,x);
+ *     t := x + s;                             ... = (x+s) rounded to integer
+ *     return t - s
+ * end;
+ *
+ * Note: Inexact will be signaled if x is not an integer, as is
+ *     customary for IEEE 754.  No other signal can be emitted.
+ */
+#ifdef VAX
+static long Lx[] = {0x5c00,0x0};               /* 2**55 */
+#define L *(double *) Lx
+#else  /* IEEE double */
+static double L = 4503599627370496.0E0;                /* 2**52 */
+#endif
+double
+rint(x)
+double x;
+{
+       double s,t,one = 1.0,copysign();
+#ifndef VAX
+       if (x != x)                             /* NaN */
+               return (x);
+#endif
+       if (copysign(x,one) >= L)               /* already an integer */
+           return (x);
+       s = copysign(L,x);
+       t = x + s;                              /* x+s rounded to integer */
+       return (t - s);
+}