A few more RBE things

rustbyexample/fn.d/closures.d/anonymity.rs

@@ -0,0 +1,14 @@
+fn apply<F>(f: F)
+where
+    F: Fn(),
+{
+    f();
+}
+
+fn main() {
+    let x = 7;
+
+    let print = || println!("{}", x);
+
+    apply(print);
+}

rustbyexample/fn.d/closures.d/input_parameters.rs

@@ -0,0 +1,36 @@
+fn apply<F>(f: F)
+where
+    F: FnOnce(),
+{
+    f();
+}
+
+fn apply_to_3<F>(f: F) -> i32
+where
+    F: Fn(i32) -> i32,
+{
+    f(3)
+}
+
+fn main() {
+    use std::mem;
+
+    let greeting = "hello";
+    let mut farewell = "goodbye".to_owned();
+
+    let diary = || {
+        println!("I said {}.", greeting);
+
+        farewell.push_str("!!!");
+        println!("Then I screamed {}.", farewell);
+        println!("Now I can sleep. zzzzz");
+
+        mem::drop(farewell);
+    };
+
+    apply(diary);
+
+    let double = |x| 2 * x;
+
+    println!("3 doubled: {}", apply_to_3(double));
+}