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src/day1/lifetimes-function-calls.rs

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+// https://google.github.io/comprehensive-rust/ownership/lifetimes-function-calls.html
+#[derive(Debug)]
+struct Point(i32, i32);
+
+// 'a is a generic parameter, it is inferred by the compiler.
+// Lifetimes start with ' and 'a is a typical default name.
+// Read &'a Point as “a borrowed Point which is valid for at least the lifetime a”.
+// The at least part is important when parameters are in different scopes.
+fn left_most<'a>(p1: &'a Point, p2: &'a Point) -> &'a Point {
+    if p1.0 < p2.0 { p1 } else { p2 }
+}
+
+fn main() {
+    let p1: Point = Point(10, 10);
+    let p2: Point = Point(20, 20);  // Put into different scope
+    let p3: &Point = left_most(&p1, &p2);
+    println!("left-most point: {:?}", p3);
+}