1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
|
//
// With tagged unions, it gets EVEN BETTER! If you don't have a
// need for a separate enum, you can define an inferred enum with
// your union all in one place. Just use the 'enum' keyword in
// place of the tag type:
//
// const Foo = union(enum) {
// small: u8,
// medium: u32,
// large: u64,
// };
//
// Let's convert Insect. Doctor Zoraptera has already deleted the
// explicit InsectStat enum for you!
//
const std = @import("std");
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 = 17 };
std.debug.print("Insect report! ", .{});
printInsect(ant);
printInsect(bee);
std.debug.print("\n", .{});
}
fn printInsect(insect: Insect) void {
switch (insect) {
.still_alive => |a| std.debug.print("Ant alive is: {}. ", .{a}),
.flowers_visited => |f| std.debug.print("Bee visited {} flowers. ", .{f}),
}
}
// Inferred enums are neat, representing the tip of the iceberg
// in the relationship between enums and unions. You can actually
// coerce a union TO an enum (which gives you the active field
// from the union as an enum). What's even wilder is that you can
// coerce an enum to a union! But don't get too excited, that
// only works when the union type is one of those weird zero-bit
// types like void!
//
// Tagged unions, as with most ideas in computer science, have a
// long history going back to the 1960s. However, they're only
// recently becoming mainstream, particularly in system-level
// programming languages. You might have also seen them called
// "variants", "sum types", or even "enums"!
|
