65 lines
1.8 KiB
Zig
65 lines
1.8 KiB
Zig
//
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// It is really quite inconvenient having to manually keep track
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// of the active field in our union, isn't it?
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//
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// Thankfully, Zig also has "tagged unions", which allow us to
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// store an enum value within our union representing which field
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// is active.
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//
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// const FooTag = enum{ small, medium, large };
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//
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// const Foo = union(FooTag) {
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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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// Now we can use a switch directly on the union to act on the
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// active field:
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//
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// var f = Foo{ .small = 10 };
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//
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// switch (f) {
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// .small => |my_small| do_something(my_small),
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// .medium => |my_medium| do_something(my_medium),
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// .large => |my_large| do_something(my_large),
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// }
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//
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// Let's make our Insects use a tagged union (Doctor Zoraptera
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// approves).
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//
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const std = @import("std");
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const InsectStat = enum { flowers_visited, still_alive };
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const Insect = union(InsectStat) {
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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 = 16 };
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std.debug.print("Insect report! ", .{});
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// Could it really be as simple as just passing the union?
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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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// By the way, did unions remind you of optional values and errors?
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// Optional values are basically "null unions" and errors use "error
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// union types". Now we can add our own unions to the mix to handle
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// whatever situations we might encounter:
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// union(Tag) { value: u32, toxic_ooze: void }
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