first commit of the new libm!

[musl] / src / math / sinh.c

diff --git a/src/math/sinh.c b/src/math/sinh.c
new file mode 100644 (file)
index 0000000..935879c
--- /dev/null
+++ b/src/math/sinh.c
@@ -0,0 +1,71 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/e_sinh.c */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunSoft, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+/* sinh(x)
+ * Method :
+ * mathematically sinh(x) if defined to be (exp(x)-exp(-x))/2
+ *      1. Replace x by |x| (sinh(-x) = -sinh(x)).
+ *      2.
+ *                                                  E + E/(E+1)
+ *          0        <= x <= 22     :  sinh(x) := --------------, E=expm1(x)
+ *                                                      2
+ *
+ *          22       <= x <= lnovft :  sinh(x) := exp(x)/2
+ *          lnovft   <= x <= ln2ovft:  sinh(x) := exp(x/2)/2 * exp(x/2)
+ *          ln2ovft  <  x           :  sinh(x) := x*shuge (overflow)
+ *
+ * Special cases:
+ *      sinh(x) is |x| if x is +INF, -INF, or NaN.
+ *      only sinh(0)=0 is exact for finite x.
+ */
+
+#include "libm.h"
+
+static const double one = 1.0, huge = 1.0e307;
+
+double sinh(double x)
+{
+       double t, h;
+       int32_t ix, jx;
+
+       /* High word of |x|. */
+       GET_HIGH_WORD(jx, x);
+       ix = jx & 0x7fffffff;
+
+       /* x is INF or NaN */
+       if (ix >= 0x7ff00000)
+               return x + x;
+
+       h = 0.5;
+       if (jx < 0) h = -h;
+       /* |x| in [0,22], return sign(x)*0.5*(E+E/(E+1))) */
+       if (ix < 0x40360000) {  /* |x|<22 */
+               if (ix < 0x3e300000)  /* |x|<2**-28 */
+                       /* raise inexact, return x */
+                       if (huge+x > one)
+                               return x;
+               t = expm1(fabs(x));
+               if (ix < 0x3ff00000)
+                       return h*(2.0*t - t*t/(t+one));
+               return h*(t + t/(t+one));
+       }
+
+       /* |x| in [22, log(maxdouble)] return 0.5*exp(|x|) */
+       if (ix < 0x40862E42)
+               return h*exp(fabs(x));
+
+       /* |x| in [log(maxdouble), overflowthresold] */
+       if (ix <= 0x408633CE)
+               return h * 2.0 * __expo2(fabs(x)); /* h is for sign only */
+
+       /* |x| > overflowthresold, sinh(x) overflow */
+       return x*huge;
+}