Add doctest example

mandelbrot/src/main.rs

@@ -80,7 +80,7 @@ fn test_parse_complex() {
 ///
 /// `bounds` is a pair giving the width and height of the image in pixels.
 /// `pixel` is a (column, row) pair indicating a particular pixel in that image.
-/// The `upper_left` and `lower_right` parameters are pionts on the complex
+/// The `upper_left` and `lower_right` parameters are points on the complex
 /// plain designating the area our image covers
 fn pixel_to_point(
     bounds: (usize, usize),

ranges/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "ranges"
+version = "0.1.0"
+authors = ["Timothy Warren <twarren@nabancard.com>"]
+edition = "2018"
+
+[dependencies]

ranges/src/lib.rs

@@ -0,0 +1,23 @@
+use std::ops::Range;
+
+/// Return true if two ranges overlap
+///
+///     assert_eq!(ranges::overlap(0..7, 3..10), true);
+///     assert_eq!(ranges::overlap(1..5, 101..105), false);
+///
+/// If either range is empty, they don't count as overlapping.
+///
+///     assert_eq!(ranges::overlap(0..0, 0..10), false);
+///
+pub fn overlap(r1: Range<usize>, r2: Range<usize>) -> bool {
+    r1.start < r1.end && r2.start < r2.end &&
+        r1.start < r2.end && r2.start < r1.end
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn it_works() {
+        assert_eq!(2 + 2, 4);
+    }
+}