add NEWS file

Author: heltonmc

NEWS.md

@@ -0,0 +1,27 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+For pre-1.0.0 releases we will increment the minor version when we export any new functions or alter exported API.
+For bug fixes, performance enhancements, or fixes to unexported functions we will increment the patch version.
+**Note**: The exported API can be considered very stable and likely will not change without serious consideration.
+
+# Unreleased
+
+### Added
+ - add an unexport method (`Bessels.besseljy(nu, x)`) for faster computation of `besselj` and `bessely` (#33)
+ - add exported methods for Hankel functions `besselh(nu, k, x)`, `hankelh1(nu, x)`, `hankelh2(nu, x)` (#33)
+
+### Fixed
+ - fix cutoff in `bessely` to not return error for integer orders and small arguments (#33)
+
+# Version 0.1.0
+
+Initial release of Bessels.jl
+
+### Added
+
+ - support bessel functions (`besselj`, `bessely`, `besseli`, `besselk`) for real arguments
+ - provide a gamma function (`Bessels.gamma`) for real arguments

src/hankel.jl

@@ -5,10 +5,10 @@
 #
 #    A numerical routine to compute both Bessel functions of the first J_{ν}(x) and second kind Y_{ν}(x)
 #    for real orders and arguments of positive or negative value. Please see notes in src/besselj.jl and src/bessely.jl
-#    for notes on implementation details as most of the routine is similar. A key difference is when the methods to compute bessely
-#    don't also give besselj, we rely on a continued fraction approach to compute J_{ν}(x)/J_{ν-1}(x) to get J_{ν}(x) [1].
-#    The continued fraction approach is in general quickly converging when nu and x are small in magnitude.
-#    When x and nu are large and nu > x we fall back to computing J_{ν}(x) and Y_{ν}(x) separately as this was found to be more efficient.
+#    for details on implementation as most of the routine is similar. A key difference is when the methods to compute bessely
+#    don't also give besselj. We then rely on a continued fraction approach to compute J_{ν}(x)/J_{ν-1}(x) to get J_{ν}(x)
+#    from  Y_{ν}(x) and Y_{ν-1}(x)[1]. The continued fraction approach is more quickly converging when nu and x are small in magnitude.
+#    When x and nu are large and nu = x + ϵ, we fall back to computing J_{ν}(x) and Y_{ν}(x) separately as this was found to be more efficient.
 #    
 # [1] Ratis, Yu L., and P. Fernández de Córdoba. "A code to calculate (high order) Bessel functions based on the continued fractions method." 
 #     Computer physics communications 76.3 (1993): 381-388.