Document return values better.

svn path=/head/; revision=176390

lib/msun/man/j0.3

@@ -28,7 +28,7 @@
 .\"     from: @(#)j0.3	6.7 (Berkeley) 4/19/91
 .\" $FreeBSD$
 .\"
-.Dd January 14, 2005
+.Dd February 18, 2008
 .Dt J0 3
 .Os
 .Sh NAME
@@ -128,10 +128,41 @@ for the positive
 value
 .Fa x .
 .Sh RETURN VALUES
-If these functions are successful,
-the computed value is returned.
+These routines return values of their respective Bessel functions.
+For large positive inputs, they may underflow and return \*(Pm0.
+.Pp
+The following applies to
+.Fn y0 ,
+.Fn y0f ,
+.Fn y1 ,
+.Fn y1f ,
+.Fn yn ,
+and
+.Fn ynf .
+If
+.Fa x
+is negative, these routines will generate an invalid exception and
+return \*(Na.
+If
+.Fa x
+is 0 or a sufficiently small positive number, these routines
+will generate an overflow exception and return -\*(If.
 .Sh SEE ALSO
 .Xr math 3
+.Sh STANDARDS
+The
+.Fn j0 ,
+.Fn j1 ,
+.Fn jn ,
+.Fn y0 ,
+.Fn y1 ,
+and
+.Fn yn
+functions conform to
+.St -p1003.1-2001 .
+The
+.Ft float
+versions are extensions.
 .Sh HISTORY
 This set of functions
 appeared in