"999 is enough for anybody" triple-zero padding (#18)

When I hit 999 exercises, I will finally have reached the ultimate
state of soteriological release and no more exercises will be needed.
The cycle will be complete. All that will be left is perfect quietude,
freedom, and highest happiness.

1 files changed, 64 insertions, 0 deletions

diff --git a/exercises/056_unions2.zig b/exercises/056_unions2.zig
new file mode 100644
index 0000000..e4294db
--- /dev/null
+++ b/exercises/056_unions2.zig
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+//
+// It is really quite inconvenient having to manually keep track
+// of the active field in our union, isn't it?
+//
+// Thankfully, Zig also has "tagged unions", which allow us to
+// store an enum value within our union representing which field
+// is active.
+//
+//     const FooTag = enum{ small, medium, large };
+//
+//     const Foo = union(FooTag) {
+//         small: u8,
+//         medium: u32,
+//         large: u64,
+//     };
+//
+// Now we can use a switch directly on the union to act on the
+// active field:
+//
+//     var f = Foo{ .small = 10 };
+//
+//     switch (f) {
+//         .small => |my_small| do_something(my_small),
+//         .medium => |my_medium| do_something(my_medium),
+//         .large => |my_large| do_something(my_large),
+//     }
+//
+// Let's make our Insects use a tagged union (Doctor Zoraptera
+// approves).
+//
+const std = @import("std");
+
+const InsectStat = enum { flowers_visited, still_alive };
+
+const Insect = union(InsectStat) {
+    flowers_visited: u16,
+    still_alive: bool,
+};
+
+pub fn main() void {
+    var ant = Insect{ .still_alive = true };
+    var bee = Insect{ .flowers_visited = 16 };
+
+    std.debug.print("Insect report! ", .{});
+
+    // Could it really be as simple as just passing the union?
+    printInsect(???);
+    printInsect(???);
+
+    std.debug.print("\n", .{});
+}
+
+fn printInsect(insect: Insect) void {
+    switch (???) {
+        .still_alive => |a| std.debug.print("Ant alive is: {}. ", .{a}),
+        .flowers_visited => |f| std.debug.print("Bee visited {} flowers. ", .{f}),
+    }
+}
+
+// By the way, did unions remind you of optional values and errors?
+// Optional values are basically "null unions" and errors use "error
+// union types". Now we can add our own unions to the mix to handle
+// whatever situations we might encounter:
+//          union(Tag) { value: u32, toxic_ooze: void }