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authornobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>2002-04-12 03:24:52 +0000
committernobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>2002-04-12 03:24:52 +0000
commitbe5524ae411e0e3165eef05142f65055f16a9837 (patch)
treef39b398f7ea3e8b1d89354c560acd74a0d17807a /missing/acosh.c
parent1aa67cb1d357af287d9ea7e764ca3c2bae2f56a8 (diff)
/tmp/log
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@2368 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Diffstat (limited to 'missing/acosh.c')
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1 files changed, 88 insertions, 0 deletions
diff --git a/missing/acosh.c b/missing/acosh.c
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+/**********************************************************************
+
+ acosh.c -
+
+ $Author$
+ $Date$
+ created at: Fri Apr 12 00:34:17 JST 2002
+
+ public domain rewrite of acosh(3), asinh(3) and atanh(3)
+
+**********************************************************************/
+
+#include <errno.h>
+#include <float.h>
+#include <math.h>
+
+/* DBL_MANT_DIG must be less than 4 times of bits of int */
+#ifdef DBL_MANT_DIG
+#define DBL_MANT_DIG 53 /* in this case, at least 12 digit precision */
+#endif
+#define BIG_CRITERIA_BIT (1<<DBL_MANT_DIG/2)
+#if BIG_CRITERIA_BIT > 0
+#define BIG_CRITERIA (1.0*BIG_CRITERIA_BIT)
+#else
+#define BIG_CRITERIA (1.0*(1<<DBL_MANT_DIG/4)*(1<<(DBL_MANT_DIG/2+1-DBL_MANT_DIG/4)))
+#endif
+#define SMALL_CRITERIA_BIT (1<<(DBL_MANT_DIG/3))
+#if SMALL_CRITERIA_BIT > 0
+#define SMALL_CRITERIA (1.0/SMALL_CRITERIA_BIT)
+#else
+#define SMALL_CRITERIA (1.0*(1<<DBL_MANT_DIG/4)*(1<<(DBL_MANT_DIG/3+1-DBL_MANT_DIG/4)))
+#endif
+
+#ifndef HAVE_ACOSH
+double
+acosh(x)
+ double x;
+{
+ if (x < 1)
+ x = -1; /* NaN */
+ else if (x == 1)
+ return 0;
+ else if (x > BIG_CRITERIA)
+ x += x;
+ else
+ x += sqrt((x + 1) * (x - 1));
+ return log(x);
+}
+#endif
+
+#ifndef HAVE_ASINH
+double
+asinh(x)
+ double x;
+{
+ int neg = x < 0;
+ double z = fabs(x);
+
+ if (z < SMALL_CRITERIA) return x;
+ if (z < (1.0/(1<<DBL_MANT_DIG/5))) {
+ double x2 = z * z;
+ z *= 1 + x2 * (-1.0/6.0 + x2 * 3.0/40.0);
+ }
+ else if (z > BIG_CRITERIA) {
+ z = log(z + z);
+ }
+ else {
+ z = log(z + sqrt(z * z + 1));
+ }
+ if (neg) z = -z;
+ return z;
+}
+#endif
+
+#ifndef HAVE_ATANH
+double
+atanh(x)
+ double x;
+{
+ int neg = x < 0;
+ double z = fabs(x);
+
+ if (z < SMALL_CRITERIA) return x;
+ z = log(z > 1 ? -1 : (1 + z) / (1 - z)) / 2;
+ if (neg) z = -z;
+ return z;
+}
+#endif