Merge commit 'upstream/4.6.1'

[debian/atlc] / src / elliptic_integral.c

diff --git a/src/elliptic_integral.c b/src/elliptic_integral.c
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+/* atlc - arbitrary transmission line calculator, for the analysis of
+transmission lines are directional couplers. 
+
+Copyright (C) 2002. Dr. David Kirkby, PhD (G8WRB).
+
+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 package_version 2
+of the License, or (at your option) any later package_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., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
+USA.
+
+Dr. David Kirkby, e-mail drkirkby at gmail.com 
+
+*/
+
+#include "config.h"
+
+#include "definitions.h"
+
+/* The following function computes:
+
+r=K(k)/K'(k) where
+K is the complete elliptic integral of the first kind,
+K' is the complementary complete elliptic integral of the first kind
+
+This simple routine was given to my by Dan  - it is one hell
+of a lot simplier than the routine in the numerical recipes book
+
+*/
+
+double K_over_Kdash(double k)
+{
+  double kp, r, kf;
+  kp = sqrt(1.0-pow(k,2.0));
+  r = 1.0;
+  kf=(1.0+k)/(1.0+kp);
+  while(kf != 1.0)
+  {
+    r = r*kf;
+    k = 2.0*sqrt(k)/(1.0+k);
+    kp = 2.0*sqrt(kp)/(1.0+kp);
+    kf=(1.0+k)/(1.0+kp);
+  }
+  return(r);
+}