1 files changed, 65 insertions, 0 deletions
diff --git a/gsl-1.9/cheb/integ.c b/gsl-1.9/cheb/integ.c
new file mode 100644
index 0000000..0f49dd9
--- /dev/null
+++ b/gsl-1.9/cheb/integ.c
@@ -0,0 +1,65 @@
+/* cheb/integ.c
+ * 
+ * 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.
+ */
+
+#include <config.h>
+#include <stdlib.h>
+#include <gsl/gsl_math.h>
+#include <gsl/gsl_errno.h>
+#include <gsl/gsl_chebyshev.h>
+
+int gsl_cheb_calc_integ(gsl_cheb_series * integ, const gsl_cheb_series * f)
+{
+  const size_t n = f->order + 1;
+  const double con = 0.25 * (f->b - f->a);
+
+  if(integ->order != f->order) 
+    {
+      GSL_ERROR ("order of chebyshev series must be equal", GSL_ENOMEM);
+    }
+
+  /* set the other parameters in the chebyshev struct */
+
+  integ->a = f->a;
+  integ->b = f->b;
+
+  /* FIXME:  should probably set integ->f[] as well */
+
+  if(n == 1) {
+    integ->c[0] = 0.;
+  }
+  else if(n == 2) {
+    integ->c[1] = con * f->c[0];
+    integ->c[0] = 2.0 * integ->c[1];
+  }
+  else {
+    double sum = 0.0;
+    double fac = 1.0;
+    size_t i;
+    for(i=1; i<=n-2; i++) {
+      integ->c[i] = con * (f->c[i-1] - f->c[i+1])/((double)i);
+      sum += fac * integ->c[i];
+      fac = -fac;
+    }
+    integ->c[n-1] = con * f->c[n-2]/(n-1.0);
+    sum += fac * integ->c[n-1];
+    integ->c[0] = 2.0 * sum;
+  }
+
+  return GSL_SUCCESS;
+}