lecture 3 stuff

lectures/03/shapes.rs

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+// how can we store circles & rectangles in a container?
+// solution 1: use an enum; static dispatch
+#[derive(Clone, Copy)]
+struct Point(f64, f64);
+
+// #[derive(Clone, Copy)]
+enum Shape {
+    Circle(Point, f64),
+    Rectangle(Point, Point),
+}
+
+fn area(s: &Shape) -> f64 {
+    match *s {
+        Shape::Circle(_p, r) => std::f64::consts::PI * r * r,
+        Shape::Rectangle(p1, p2) => ((p1.1 - p2.1) * (p1.0 - p2.0)).abs(),
+    }
+}
+
+fn total_area(v: &[Shape]) -> f64 {
+    let mut total = 0.0;
+
+    for s in v {
+        total += area(s);
+    }
+    total
+}
+
+fn main() {
+    let v: Vec<Shape> = vec![ 
+        Shape::Circle(Point(0.0, 0.0), 1.0),
+        Shape::Rectangle(Point(1.0, 1.0), Point(2.0, 3.0)),
+    ];
+    println!("{}", total_area(&v));
+}
+