From 7ce331c01ce6eb7b3f5c715a38a24359da9c6ee2 Mon Sep 17 00:00:00 2001
From: Eric Andersen <andersen@codepoet.org>
Date: Thu, 22 Nov 2001 14:04:29 +0000
Subject: Totally rework the math library, this time based on the MacOs X math
 library (which is itself based on the math lib from FreeBSD).  -Erik

---
 libm/w_jn.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100644 libm/w_jn.c

(limited to 'libm/w_jn.c')

diff --git a/libm/w_jn.c b/libm/w_jn.c
new file mode 100644
index 000000000..20ba79beb
--- /dev/null
+++ b/libm/w_jn.c
@@ -0,0 +1,92 @@
+/* @(#)w_jn.c 5.1 93/09/24 */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice 
+ * is preserved.
+ * ====================================================
+ */
+
+#if defined(LIBM_SCCS) && !defined(lint)
+static char rcsid[] = "$NetBSD: w_jn.c,v 1.6 1995/05/10 20:49:19 jtc Exp $";
+#endif
+
+/*
+ * wrapper jn(int n, double x), yn(int n, double x)
+ * floating point Bessel's function of the 1st and 2nd kind
+ * of order n
+ *          
+ * Special cases:
+ *	y0(0)=y1(0)=yn(n,0) = -inf with division by zero signal;
+ *	y0(-ve)=y1(-ve)=yn(n,-ve) are NaN with invalid signal.
+ * Note 2. About jn(n,x), yn(n,x)
+ *	For n=0, j0(x) is called,
+ *	for n=1, j1(x) is called,
+ *	for n<x, forward recursion us used starting
+ *	from values of j0(x) and j1(x).
+ *	for n>x, a continued fraction approximation to
+ *	j(n,x)/j(n-1,x) is evaluated and then backward
+ *	recursion is used starting from a supposed value
+ *	for j(n,x). The resulting value of j(0,x) is
+ *	compared with the actual value to correct the
+ *	supposed value of j(n,x).
+ *
+ *	yn(n,x) is similar in all respects, except
+ *	that forward recursion is used for all
+ *	values of n>1.
+ *	
+ */
+
+#include "math.h"
+#include "math_private.h"
+
+#ifdef __STDC__
+	double jn(int n, double x)	/* wrapper jn */
+#else
+	double jn(n,x)			/* wrapper jn */
+	double x; int n;
+#endif
+{
+#ifdef _IEEE_LIBM
+	return __ieee754_jn(n,x);
+#else
+	double z;
+	z = __ieee754_jn(n,x);
+	if(_LIB_VERSION == _IEEE_ || isnan(x) ) return z;
+	if(fabs(x)>X_TLOSS) {
+	    return __kernel_standard((double)n,x,38); /* jn(|x|>X_TLOSS,n) */
+	} else
+	    return z;
+#endif
+}
+
+#ifdef __STDC__
+	double yn(int n, double x)	/* wrapper yn */
+#else
+	double yn(n,x)			/* wrapper yn */
+	double x; int n;
+#endif
+{
+#ifdef _IEEE_LIBM
+	return __ieee754_yn(n,x);
+#else
+	double z;
+	z = __ieee754_yn(n,x);
+	if(_LIB_VERSION == _IEEE_ || isnan(x) ) return z;
+        if(x <= 0.0){
+                if(x==0.0)
+                    /* d= -one/(x-x); */
+                    return __kernel_standard((double)n,x,12);
+                else
+                    /* d = zero/(x-x); */
+                    return __kernel_standard((double)n,x,13);
+        }
+	if(x>X_TLOSS) {
+	    return __kernel_standard((double)n,x,39); /* yn(x>X_TLOSS,n) */
+	} else
+	    return z;
+#endif
+}
-- 
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