1 files changed, 36 insertions, 0 deletions
diff --git a/gsl-1.9/interpolation/integ_eval.h b/gsl-1.9/interpolation/integ_eval.h
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+++ b/gsl-1.9/interpolation/integ_eval.h
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+/* interpolation/integ_eval_macro.h
+ * 
+ * Copyright (C) 1996, 1997, 1998, 1999, 2000 Gerard Jungman
+ * 
+ * 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.
+ */
+
+/* function for doing the spline integral evaluation
+   which is common to both the cspline and akima methods
+ */
+
+static inline double
+integ_eval (double ai, double bi, double ci, double di, double xi, double a,
+            double b)
+{
+  const double r1 = a - xi;
+  const double r2 = b - xi;
+  const double r12 = r1 + r2;
+  const double bterm = 0.5 * bi * r12;
+  const double cterm = (1.0 / 3.0) * ci * (r1 * r1 + r2 * r2 + r1 * r2);
+  const double dterm = 0.25 * di * r12 * (r1 * r1 + r2 * r2);
+
+  return (b - a) * (ai + bterm + cterm + dterm);
+}