added lifetimes example

Author: BartMassey

README.md

@@ -56,3 +56,4 @@ in a controlled repository now.
 * `enum-example.rs`: example of Rust enum
 * `closure-example.rs`: example of Rust closure
 * `iterator-example.rs`: example of Rust iterator
+* `lifetimes-example.rs`: example involving Rust lifetimes

lifetimes-example.rs

@@ -0,0 +1,43 @@
+struct Halves<'a, 'b, T> {
+    first: &'a [T],
+    last: &'b [T],
+}
+
+/*
+fn half<'a, T>(source: &'a [T]) -> Halves<'a, 'a, T> {
+    let halfway = source.len() / 2;
+    Halves {
+        first: &source[..halfway],
+        last: &source[halfway..],
+    }
+}
+*/
+
+fn swap<'a, 'b, T>(source: Halves<'a, 'b, T>) -> Halves<'b, 'a, T> {
+    Halves {
+        first: source.last,
+        last: source.first,
+    }
+}
+
+/*
+fn longer(s: String, t: String) -> String {
+    if s.len() >= t.len() {
+        s
+    } else {
+        t
+    }
+}
+*/
+
+fn main() {
+    // let halves = half(&[1, 2, 3, 4, 5]);
+    let first = vec![1, 2];
+    let last = vec![3, 4, 5];
+    let halves = Halves { first: &first, last: &last };
+    let swapped = swap(halves);
+    let new_first = swapped.first;
+    drop(swapped);
+    //drop(first);
+    println!("{:?}", new_first);
+}