methods on a struct

src/main.rs

@@ -1,28 +1,24 @@
 fn main() {
-    fizzbuzz_to(20); // defined below. No forward declaration needed.
+    let mut rect = Rectangle {
+        width: 10,
+        height: 5,
+    };
+    println!("old area: {}", rect.area());
+    rect.inc_width(5);
+    println!("new area: {}", rect.area());
 }
 
-fn is_divisible_by(lhs: u32, rhs: u32) -> bool {
-    // returns a boolean
-    if rhs == 0 {
-        return false;
-    }
-    return lhs % rhs == 0;
+struct Rectangle {
+    width: u32,
+    height: u32,
 }
 
-fn fizzbuzz(n: u32) -> () {
-    // this returns nothing, so '()'
-    match (is_divisible_by(n, 3), is_divisible_by(n, 5)) {
-        (true, true) => println!("fizzbuzz"),
-        (true, false) => println!("fizz"),
-        (false, true) => println!("buzz"),
-        (false, false) => println!("{n}"),
+impl Rectangle {
+    fn area(&self) -> u32 {
+        return self.width * self.height;
     }
-}
 
-fn fizzbuzz_to(n: u32) {
-    // like above, but you can omit the '()'
-    for n in 1..=n {
-        fizzbuzz(n);
+    fn inc_width(&mut self, delta: u32) {
+        self.width += delta;
     }
 }