Add example of when the functions are None

Bump version number, add changes to log

CHANGELOG.md

@@ -1,3 +1,7 @@
+# 0.2.3
+
+ - Documentation improvements.
+
 # 0.2.2
 
  - Minor documentation improvements.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "lambert_w"
-version = "0.2.2"
+version = "0.2.3"
 edition = "2021"
 authors = ["Johanna Sörngård <[email protected]>"]
 categories = ["mathematics"]

src/accurate/mod.rs

@@ -12,8 +12,9 @@ use super::Z0;
 ///
 /// Uses the piecewise minimax rational function approximation method of Toshio Fukushima.
 ///
-/// # Example
+/// # Examples
 ///
+/// Basic usage:
 /// ```
 /// use lambert_w::accurate::lambert_w_0;
 ///
@@ -24,6 +25,11 @@ use super::Z0;
 ///
 /// assert_abs_diff_eq!(w, 1.0736581947961492);
 /// ```
+/// Too small arguments result in `None`:
+/// ```
+/// # use lambert_w::accurate::lambert_w_0;
+/// assert_eq!(lambert_w_0(-1.0), None);
+/// ```
 pub fn lambert_w_0(z: f64) -> Option<f64> {
     dw0c(z - Z0)
 }
@@ -32,8 +38,9 @@ pub fn lambert_w_0(z: f64) -> Option<f64> {
 ///
 /// Uses the piecewise minimax rational function approximation method of Toshio Fukushima.
 ///
-/// # Example
+/// # Examples
 ///
+/// Basic usage:
 /// ```
 /// use lambert_w::accurate::lambert_w_m1;
 ///
@@ -44,6 +51,12 @@ pub fn lambert_w_0(z: f64) -> Option<f64> {
 ///
 /// assert_abs_diff_eq!(w,  -1.6385284199703634);
 /// ```
+/// Too small or positive arguments result in `None`:
+/// ```
+/// # use lambert_w::accurate::lambert_w_m1;
+/// assert_eq!(lambert_w_m1(-1.0), None);
+/// assert_eq!(lambert_w_m1(1.0), None);
+/// ```
 pub fn lambert_w_m1(z: f64) -> Option<f64> {
     dwm1c(z, z - Z0)
 }

src/fast/mod.rs

@@ -10,8 +10,9 @@ use swm1::swm1;
 ///
 /// Uses the piecewise minimax rational function approximation method of Toshio Fukushima.
 ///
-/// # Example
+/// # Examples
 ///
+/// Basic usage:
 /// ```
 /// use lambert_w::fast::lambert_w_0;
 ///
@@ -22,6 +23,11 @@ use swm1::swm1;
 ///
 /// assert_abs_diff_eq!(w, 1.0736581947961492, epsilon = 1e-7);
 /// ```
+/// Too small arguments result in `None`:
+/// ```
+/// # use lambert_w::fast::lambert_w_0;
+/// assert_eq!(lambert_w_0(-1.0), None);
+/// ```
 pub fn lambert_w_0(z: f64) -> Option<f64> {
     sw0(z)
 }
@@ -30,8 +36,9 @@ pub fn lambert_w_0(z: f64) -> Option<f64> {
 ///
 /// Uses the piecewise minimax rational function approximation method of Toshio Fukushima.
 ///
-/// # Example
+/// # Examples
 ///
+/// Basic usage:
 /// ```
 /// use lambert_w::fast::lambert_w_m1;
 ///
@@ -42,6 +49,12 @@ pub fn lambert_w_0(z: f64) -> Option<f64> {
 ///
 /// assert_abs_diff_eq!(w, -1.6385284199703634, epsilon = 1e-7);
 /// ```
+/// Too small or positive arguments result in `None`:
+/// ```
+/// # use lambert_w::fast::lambert_w_m1;
+/// assert_eq!(lambert_w_m1(-1.0), None);
+/// assert_eq!(lambert_w_m1(1.0), None);
+/// ```
 pub fn lambert_w_m1(z: f64) -> Option<f64> {
     swm1(z)
 }