1 files changed, 102 insertions, 0 deletions
diff --git a/gsl-1.9/sys/invhyp.c b/gsl-1.9/sys/invhyp.c
new file mode 100644
index 0000000..346c8a4
--- /dev/null
+++ b/gsl-1.9/sys/invhyp.c
@@ -0,0 +1,102 @@
+/* sys/invhyp.c
+ * 
+ * Copyright (C) 1996, 1997, 1998, 1999, 2000 Brian Gough
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or (at
+ * your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include <config.h>
+#include <math.h>
+#include <gsl/gsl_math.h>
+#include <gsl/gsl_machine.h>
+
+double
+gsl_acosh (const double x)
+{
+  if (x > 1.0 / GSL_SQRT_DBL_EPSILON)
+    {
+      return log (x) + M_LN2;
+    }
+  else if (x > 2)
+    {
+      return log (2 * x - 1 / (sqrt (x * x - 1) + x));
+    }
+  else if (x > 1)
+    {
+      double t = x - 1;
+      return log1p (t + sqrt (2 * t + t * t));
+    }
+  else if (x == 1)
+    {
+      return 0;
+    }
+  else
+    {
+      return GSL_NAN;
+    }
+}
+
+double
+gsl_asinh (const double x)
+{
+  double a = fabs (x);
+  double s = (x < 0) ? -1 : 1;
+
+  if (a > 1 / GSL_SQRT_DBL_EPSILON)
+    {
+      return s * (log (a) + M_LN2);
+    }
+  else if (a > 2)
+    {
+      return s * log (2 * a + 1 / (a + sqrt (a * a + 1)));
+    }
+  else if (a > GSL_SQRT_DBL_EPSILON)
+    {
+      double a2 = a * a;
+      return s * log1p (a + a2 / (1 + sqrt (1 + a2)));
+    }
+  else
+    {
+      return x;
+    }
+}
+
+double
+gsl_atanh (const double x)
+{
+  double a = fabs (x);
+  double s = (x < 0) ? -1 : 1;
+
+  if (a > 1)
+    {
+      return GSL_NAN;
+    }
+  else if (a == 1)
+    {
+      return (x < 0) ? GSL_NEGINF : GSL_POSINF;
+    }
+  else if (a >= 0.5)
+    {
+      return s * 0.5 * log1p (2 * a / (1 - a));
+    }
+  else if (a > GSL_DBL_EPSILON)
+    {
+      return s * 0.5 * log1p (2 * a + 2 * a * a / (1 - a));
+    }
+  else
+    {
+      return x;
+    }
+}