aboutsummaryrefslogtreecommitdiff
path: root/sysdeps/ieee754/ldbl-128ibm/e_acoshl.c
diff options
context:
space:
mode:
Diffstat (limited to 'sysdeps/ieee754/ldbl-128ibm/e_acoshl.c')
-rw-r--r--sysdeps/ieee754/ldbl-128ibm/e_acoshl.c69
1 files changed, 69 insertions, 0 deletions
diff --git a/sysdeps/ieee754/ldbl-128ibm/e_acoshl.c b/sysdeps/ieee754/ldbl-128ibm/e_acoshl.c
new file mode 100644
index 0000000000..00576c76c8
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-128ibm/e_acoshl.c
@@ -0,0 +1,69 @@
+/* @(#)e_acosh.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.
+ * ====================================================
+ */
+
+#if defined(LIBM_SCCS) && !defined(lint)
+static char rcsid[] = "$NetBSD: e_acosh.c,v 1.9 1995/05/12 04:57:18 jtc Exp $";
+#endif
+
+/* __ieee754_acosh(x)
+ * Method :
+ * Based on
+ * acosh(x) = log [ x + sqrt(x*x-1) ]
+ * we have
+ * acosh(x) := log(x)+ln2, if x is large; else
+ * acosh(x) := log(2x-1/(sqrt(x*x-1)+x)) if x>2; else
+ * acosh(x) := log1p(t+sqrt(2.0*t+t*t)); where t=x-1.
+ *
+ * Special cases:
+ * acosh(x) is NaN with signal if x<1.
+ * acosh(NaN) is NaN without signal.
+ */
+
+#include "math.h"
+#include "math_private.h"
+
+#ifdef __STDC__
+static const long double
+#else
+static long double
+#endif
+one = 1.0L,
+ln2 = 6.93147180559945286227e-01L; /* 0x3FE62E42, 0xFEFA39EF */
+
+#ifdef __STDC__
+ long double __ieee754_acoshl(long double x)
+#else
+ long double __ieee754_acoshl(x)
+ long double x;
+#endif
+{
+ long double t;
+ int64_t hx;
+ u_int64_t lx;
+ GET_LDOUBLE_WORDS64(hx,lx,x);
+ if(hx<0x3ff0000000000000LL) { /* x < 1 */
+ return (x-x)/(x-x);
+ } else if(hx >=0x41b0000000000000LL) { /* x > 2**28 */
+ if(hx >=0x7ff0000000000000LL) { /* x is inf of NaN */
+ return x+x;
+ } else
+ return __ieee754_logl(x)+ln2; /* acosh(huge)=log(2x) */
+ } else if (((hx-0x3ff0000000000000LL)|(lx&0x7fffffffffffffffLL))==0) {
+ return 0.0; /* acosh(1) = 0 */
+ } else if (hx > 0x4000000000000000LL) { /* 2**28 > x > 2 */
+ t=x*x;
+ return __ieee754_logl(2.0*x-one/(x+__ieee754_sqrtl(t-one)));
+ } else { /* 1<x<2 */
+ t = x-one;
+ return __log1p(t+__sqrtl(2.0*t+t*t));
+ }
+}