1 files changed, 131 insertions, 0 deletions
diff --git a/gsl-1.9/specfunc/bessel_Ynu.c b/gsl-1.9/specfunc/bessel_Ynu.c
new file mode 100644
index 0000000..1abcf7b
--- /dev/null
+++ b/gsl-1.9/specfunc/bessel_Ynu.c
@@ -0,0 +1,131 @@
+/* specfunc/bessel_Ynu.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.
+ */
+
+/* Author:  G. Jungman */
+
+#include <config.h>
+#include <gsl/gsl_math.h>
+#include <gsl/gsl_errno.h>
+#include <gsl/gsl_sf_bessel.h>
+
+#include "error.h"
+
+#include "bessel.h"
+#include "bessel_olver.h"
+#include "bessel_temme.h"
+
+/* Perform forward recurrence for Y_nu(x) and Y'_nu(x)
+ *
+ *        Y_{nu+1} =  nu/x Y_nu - Y'_nu
+ *       Y'_{nu+1} = -(nu+1)/x Y_{nu+1} + Y_nu
+ */
+#if 0
+static
+int
+bessel_Y_recur(const double nu_min, const double x, const int kmax,
+               const double Y_start, const double Yp_start,
+               double * Y_end, double * Yp_end)
+{
+  double x_inv = 1.0/x;
+  double nu = nu_min;
+  double Y_nu  = Y_start;
+  double Yp_nu = Yp_start;
+  int k;
+
+  for(k=1; k<=kmax; k++) {
+    double nuox = nu*x_inv;
+    double Y_nu_save = Y_nu;
+    Y_nu  = -Yp_nu + nuox * Y_nu;
+    Yp_nu = Y_nu_save - (nuox+x_inv) * Y_nu;
+    nu += 1.0;
+  }
+  *Y_end  = Y_nu;
+  *Yp_end = Yp_nu;
+  return GSL_SUCCESS;
+}
+#endif
+
+
+/*-*-*-*-*-*-*-*-*-*-*-* Functions with Error Codes *-*-*-*-*-*-*-*-*-*-*-*/
+
+int
+gsl_sf_bessel_Ynu_e(double nu, double x, gsl_sf_result * result)
+{
+  /* CHECK_POINTER(result) */
+
+  if(x <= 0.0 || nu < 0.0) {
+    DOMAIN_ERROR(result);
+  }
+  else if(nu > 50.0) {
+    return gsl_sf_bessel_Ynu_asymp_Olver_e(nu, x, result);
+  }
+  else {
+    /* -1/2 <= mu <= 1/2 */
+    int N = (int)(nu + 0.5);
+    double mu = nu - N;
+
+    gsl_sf_result Y_mu, Y_mup1;
+    int stat_mu;
+    double Ynm1;
+    double Yn;
+    double Ynp1;
+    int n;
+
+    if(x < 2.0) {
+      /* Determine Ymu, Ymup1 directly. This is really
+       * an optimization since this case could as well
+       * be handled by a call to gsl_sf_bessel_JY_mu_restricted(),
+       * as below.
+       */
+      stat_mu = gsl_sf_bessel_Y_temme(mu, x, &Y_mu, &Y_mup1);
+    }
+    else {
+      /* Determine Ymu, Ymup1 and Jmu, Jmup1.
+       */
+      gsl_sf_result J_mu, J_mup1;
+      stat_mu = gsl_sf_bessel_JY_mu_restricted(mu, x, &J_mu, &J_mup1, &Y_mu, &Y_mup1);
+    }
+
+    /* Forward recursion to get Ynu, Ynup1.
+     */
+    Ynm1 = Y_mu.val;
+    Yn   = Y_mup1.val;
+    for(n=1; n<=N; n++) {
+      Ynp1 = 2.0*(mu+n)/x * Yn - Ynm1;
+      Ynm1 = Yn;
+      Yn   = Ynp1;
+    }
+
+    result->val  = Ynm1; /* Y_nu */
+    result->err  = (N + 1.0) * fabs(Ynm1) * (fabs(Y_mu.err/Y_mu.val) + fabs(Y_mup1.err/Y_mup1.val));
+    result->err += 2.0 * GSL_DBL_EPSILON * fabs(Ynm1);
+
+    return stat_mu;
+  }
+}
+
+
+/*-*-*-*-*-*-*-*-*-* Functions w/ Natural Prototypes *-*-*-*-*-*-*-*-*-*-*/
+
+#include "eval.h"
+
+double gsl_sf_bessel_Ynu(const double nu, const double x)
+{
+  EVAL_RESULT(gsl_sf_bessel_Ynu_e(nu, x, &result));
+}