Add solution sheet8

aufgaben/sheet8/sol1/times.rs

@@ -0,0 +1,19 @@
+fn main() {
+    3.times(|i| {
+        println!("Ferris ate {} cookies", i);
+    });
+}
+
+trait ChristmasExt<T> {
+    fn times<F: FnMut(T)>(&self, f: F);
+}
+
+// We would somehow implement this for all integer types, but this is just
+// a proof of concept, so one impl for `i32` is fine.
+impl ChristmasExt<i32> for i32 {
+    fn times<F: FnMut(i32)>(&self, mut f: F) {
+        for i in 0..*self {
+            f(i);
+        }
+    }
+}