optionals done

exercises/045_optionals.zig

@@ -29,7 +29,7 @@ pub fn main() void {
 
     // Please threaten the result so that answer is either the
     // integer value from deepThought() OR the number 42:
-    const answer: u8 = result;
+    const answer: u8 = result orelse 42;
 
     std.debug.print("The Ultimate Answer: {}.\n", .{answer});
 }

exercises/046_optionals2.zig

@@ -22,7 +22,7 @@ const std = @import("std");
 
 const Elephant = struct {
     letter: u8,
-    tail: *Elephant = null, // Hmm... tail needs something...
+    tail: ?*Elephant = null, // Hmm... tail needs something...
     visited: bool = false,
 };
 
@@ -63,9 +63,12 @@ fn visitElephants(first_elephant: *Elephant) void {
         // We should stop once we encounter a tail that
         // does NOT point to another element. What can
         // we put here to make that happen?
+        if (e.tail == null) {
+            break;
+        }
 
         // HINT: We want something similar to what `.?` does,
         // but instead of ending the program, we want to exit the loop...
-        e = e.tail ???
+        e = e.tail.?;
     }
 }