Add solution sheet9

aufgaben/sheet9/sol1/try-opt.rs

@@ -0,0 +1,36 @@
+// If we would make this public for everyone, we would need to use absolute
+// paths!
+macro_rules! try_opt {
+    ($e:expr) => {
+        match $e {
+            ::std::option::Option::Some(v) => v,
+            None => return None,
+        }
+    }
+}
+
+macro_rules! name {
+    () => ($crate)
+}
+
+fn main() {
+    println!("{:?}", name!());
+    println!("consistent: {:?}", is_home_consistent());
+    println!("dummy: {:?}", foo());
+}
+
+fn foo() -> Option<u8> {
+    let a: u8 = try_opt!(Some(50));
+    let b = try_opt!(a.checked_mul(6));
+
+    Some(b / 2)
+}
+
+fn is_home_consistent() -> Option<bool> {
+    use std::env;
+
+    let home_dir = try_opt!(env::home_dir());
+    let home_var = try_opt!(env::var_os("HOME"));
+
+    Some(home_dir == home_var)
+}