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89 lines
2.4 KiB
Zig
89 lines
2.4 KiB
Zig
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//
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// Remeber excerice xx with tagged unions. That was a lot more better
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// but it's can bee perfect.
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//
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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 Ant = struct {
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still_alive: bool,
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pub fn print(self: Ant) void {
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std.debug.print("Ant is {s}.\n", .{if (self.still_alive) "alive" else "death"});
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}
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};
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const Bee = struct {
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flowers_visited: u16,
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pub fn print(self: Bee) void {
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std.debug.print("Bee visited {} flowers.\n", .{self.flowers_visited});
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}
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};
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const Grasshopper = struct {
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distance_hopped: u16,
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pub fn print(self: Grasshopper) void {
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std.debug.print("Grasshopper hopped {} m.\n", .{self.distance_hopped});
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}
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};
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const Insect = union(enum) {
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ant: Ant,
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bee: Bee,
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grasshopper: Grasshopper,
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pub fn print(self: Insect) void {
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switch (self) {
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inline else => |case| return case.print(),
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}
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}
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};
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pub fn main() !void {
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var my_insects = [_]Insect{ Insect{
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.ant = Ant{ .still_alive = true },
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}, Insect{
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.bee = Bee{ .flowers_visited = 17 },
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}, Insect{
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.grasshopper = Grasshopper{ .distance_hopped = 32 },
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} };
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try dailyReport(&my_insects);
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}
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fn dailyReport(insectReport: []Insect) !void {
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std.debug.print("Daily insect report:\n", .{});
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for (insectReport) |insect| {
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insect.print();
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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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