1 files changed, 111 insertions, 0 deletions
diff --git a/gsl-1.9/specfunc/bessel_J0.c b/gsl-1.9/specfunc/bessel_J0.c
new file mode 100644
index 0000000..24969f6
--- /dev/null
+++ b/gsl-1.9/specfunc/bessel_J0.c
@@ -0,0 +1,111 @@
+/* specfunc/bessel_J0.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_mode.h>
+#include "bessel.h"
+#include "bessel_amp_phase.h"
+#include <gsl/gsl_sf_trig.h>
+#include <gsl/gsl_sf_bessel.h>
+
+#include "cheb_eval.c"
+
+/*-*-*-*-*-*-*-*-*-*-*-* Private Section *-*-*-*-*-*-*-*-*-*-*-*/
+
+
+/* based on SLATEC besj0, 1977 version, w. fullerton */
+
+/* chebyshev expansions for Bessel functions
+
+ series for bj0        on the interval  0.          to  1.60000d+01
+                                        with weighted error   7.47e-18
+                                         log weighted error  17.13
+                               significant figures required  16.98
+                                    decimal places required  17.68
+
+*/
+
+static double bj0_data[13] = {
+   0.100254161968939137, 
+  -0.665223007764405132, 
+   0.248983703498281314, 
+  -0.0332527231700357697,
+   0.0023114179304694015,
+  -0.0000991127741995080,
+   0.0000028916708643998,
+  -0.0000000612108586630,
+   0.0000000009838650793,
+  -0.0000000000124235515,
+   0.0000000000001265433,
+  -0.0000000000000010619,
+   0.0000000000000000074,
+};
+static cheb_series bj0_cs = {
+  bj0_data,
+  12,
+  -1, 1,
+  9
+};
+
+
+/*-*-*-*-*-*-*-*-*-*-*-* Functions with Error Codes *-*-*-*-*-*-*-*-*-*-*-*/
+
+int gsl_sf_bessel_J0_e(const double x, gsl_sf_result * result)
+{
+  double y = fabs(x);
+
+  /* CHECK_POINTER(result) */
+
+  if(y < 2.0*GSL_SQRT_DBL_EPSILON) {
+    result->val = 1.0;
+    result->err = y*y;
+    return GSL_SUCCESS;
+  }
+  else if(y <= 4.0) {
+    return cheb_eval_e(&bj0_cs, 0.125*y*y - 1.0, result);
+  }
+  else {
+    const double z = 32.0/(y*y) - 1.0;
+    gsl_sf_result ca;
+    gsl_sf_result ct;
+    gsl_sf_result cp;
+    const int stat_ca = cheb_eval_e(&_gsl_sf_bessel_amp_phase_bm0_cs,  z, &ca);
+    const int stat_ct = cheb_eval_e(&_gsl_sf_bessel_amp_phase_bth0_cs, z, &ct);
+    const int stat_cp = gsl_sf_bessel_cos_pi4_e(y, ct.val/y, &cp);
+    const double sqrty = sqrt(y);
+    const double ampl  = (0.75 + ca.val) / sqrty;
+    result->val  = ampl * cp.val;
+    result->err  = fabs(cp.val) * ca.err/sqrty + fabs(ampl) * cp.err;
+    result->err += GSL_DBL_EPSILON * fabs(result->val);
+    return GSL_ERROR_SELECT_3(stat_ca, stat_ct, stat_cp);
+  }
+}
+
+/*-*-*-*-*-*-*-*-*-* Functions w/ Natural Prototypes *-*-*-*-*-*-*-*-*-*-*/
+
+#include "eval.h"
+
+double gsl_sf_bessel_J0(const double x)
+{
+  EVAL_RESULT(gsl_sf_bessel_J0_e(x, &result));
+}