55 lines
1.7 KiB
Zig
55 lines
1.7 KiB
Zig
//
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// With tagged unions, it gets EVEN BETTER! If you don't have a
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// need for a separate enum, you can define an inferred enum with
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// your union all in one place. Just use the 'enum' keyword in
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// place of the tag type:
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//
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// const Foo = union(enum) {
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// small: u8,
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// medium: u32,
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// large: u64,
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// };
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//
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// Let's convert Insect. Doctor Zoraptera has already deleted the
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// explicit InsectStat enum for you!
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//
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const std = @import("std");
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const Insect = union(enum) {
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flowers_visited: u16,
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still_alive: bool,
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};
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pub fn main() void {
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var ant = Insect{ .still_alive = true };
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var bee = Insect{ .flowers_visited = 17 };
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std.debug.print("Insect report! ", .{});
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printInsect(ant);
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printInsect(bee);
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std.debug.print("\n", .{});
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}
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fn printInsect(insect: Insect) void {
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switch (insect) {
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.still_alive => |a| std.debug.print("Ant alive is: {}. ", .{a}),
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.flowers_visited => |f| std.debug.print("Bee visited {} flowers. ", .{f}),
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}
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}
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// Inferred enums are neat, representing the tip of the iceberg
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// in the relationship between enums and unions. You can actually
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// coerce a union TO an enum (which gives you the active field
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// from the union as an enum). What's even wilder is that you can
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// coerce an enum to a union! But don't get too excited, that
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// only works when the union type is one of those weird zero-bit
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// types like void!
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//
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// Tagged unions, as with most ideas in computer science, have a
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// long history going back to the 1960s. However, they're only
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// recently becoming mainstream, particularly in system-level
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// programming languages. You might have also seen them called
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// "variants", "sum types", or even "enums"!
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