Added ex 48, additional comment on 46

exercises/48_methods2.zig

@@ -0,0 +1,68 @@
+//
+// Now that we've seen how methods work, let's see if we can help
+// our elephants out a bit more with some Elephant methods.
+//
+const std = @import("std");
+
+const Elephant = struct {
+    letter: u8,
+    tail: ?*Elephant = null,
+    visited: bool = false,
+
+    // New Elephant methods!
+    pub fn getTail(self: *Elephant) *Elephant {
+        return self.tail.?; // Remember, this is means "orelse unreachable"
+    }
+
+    pub fn hasTail(self: *Elephant) bool {
+        return (self.tail != null);
+    }
+
+    pub fn visit(self: *Elephant) void {
+        self.visited = true;
+    }
+
+    pub fn print(self: *Elephant) void {
+        // Prints elephant letter and (V)isited or (U)nvisited.
+        var v: u8 = if (self.visited) 'V' else 'U';
+        std.debug.print("Elephant {u} ({u}). ", .{ self.letter, v});
+    }
+};
+
+pub fn main() void {
+    var elephantA = Elephant{ .letter = 'A' };
+    var elephantB = Elephant{ .letter = 'B' };
+    var elephantC = Elephant{ .letter = 'C' };
+
+    // Link the elephants so that each tail "points" to the next.
+    elephantA.tail = &elephantB;
+    elephantB.tail = &elephantC;
+
+    visitElephants(&elephantA);
+
+    std.debug.print("\n", .{});
+}
+
+// This function visits all elephants once, starting with the
+// first elephant and following the tails to the next elephant.
+fn visitElephants(first_elephant: *Elephant) void {
+    var e = first_elephant;
+
+    while (true) {
+        e.print();
+        e.visit();
+
+        // Get the next elephant or stop.
+        if (e.hasTail()) {
+            e = e.???; // Which method do we want here?
+        } else {
+            break;
+        }
+    }
+}
+
+// Bonus: Zig's enums can also have methods! Can you find
+// one in the wild? If you can, mention it along with your
+// name or alias in a comment below this one and make a
+// pull request on GitHub for a piece of eternal Ziglings
+// glory. The first five (5) PRs will be accepted!