diff options
| -rw-r--r-- | README.md | 5 | ||||
| -rw-r--r-- | build.zig | 8 | ||||
| -rw-r--r-- | exercises/108_labeled_switch.zig | 77 | ||||
| -rw-r--r-- | patches/patches/108_labeled_switch.patch | 18 |
4 files changed, 105 insertions, 3 deletions
@@ -88,7 +88,8 @@ that if you update one, you may need to also update the other. ### Version Changes -Version-0.14.0-dev.1224 +Version-0.14.0-dev.1573 +* *2024-09-16* zig 0.14.0-dev.1573 - introduction of labeled switch, see [#21257](https://github.com/ziglang/zig/pull/21257) * *2024-09-02* zig 0.14.0-dev.1409 - several changes in std.builtin, see [#21225](https://github.com/ziglang/zig/pull/21225) * *2024-08-04* zig 0.14.0-dev.1224 - several changes in build system, see [#21115](https://github.com/ziglang/zig/pull/21115) * *2024-08-04* zig 0.14.0-dev.839 - several changes in build system, see [#20580](https://github.com/ziglang/zig/pull/20580), [#20600](https://github.com/ziglang/zig/issues/20600) @@ -229,7 +230,7 @@ Zig Core Language * [X] Bit manipulation * [X] Working with C * [X] Threading -* [ ] Labeled switch (#21257) +* [x] Labeled switch Zig Standard Library @@ -15,7 +15,7 @@ const print = std.debug.print; // 1) Getting Started // 2) Version Changes comptime { - const required_zig = "0.14.0-dev.1409"; + const required_zig = "0.14.0-dev.1573"; const current_zig = builtin.zig_version; const min_zig = std.SemanticVersion.parse(required_zig) catch unreachable; if (current_zig.order(min_zig) == .lt) { @@ -1198,6 +1198,12 @@ const exercises = [_]Exercise{ , }, .{ + .main_file = "108_labeled_switch.zig", + .output = + \\The pull request has been merged + , + }, + .{ .main_file = "999_the_end.zig", .output = \\ diff --git a/exercises/108_labeled_switch.zig b/exercises/108_labeled_switch.zig new file mode 100644 index 0000000..0748d9d --- /dev/null +++ b/exercises/108_labeled_switch.zig @@ -0,0 +1,77 @@ +// +// You've heard of while loops in exercises 011,012,013 and 014 +// You've also heard of switch expressions in exercises 030 and 31. +// You've also seen how labels can be used in exercise 063. +// +// By combining while loops and switch statements with continue and break statements +// one can create very concise State Machines. +// +// One such example would be: +// +// pub fn main() void { +// var op: u8 = 1; +// while (true) { +// switch (op) { +// 1 => { op = 2; continue; }, +// 2 => { op = 3; continue; }, +// 3 => return, +// 4 => {}, +// } +// break; +// } +// std.debug.print("This statement cannot be reached"); +// } +// +// By combining all we've learned so far, we can now proceed with a labeled switch +// +// A labeled switch is some extra syntatic sugar, which comes with all sorts of +// candy (performance benefits). Don't believe me? Directly to source https://github.com/ziglang/zig/pull/21367 +// +// Here is the previous excerpt implemented as a labeled switch instead: +// +// pub fn main() void { +// foo: switch (@as(u8, 1)) { +// 1 => continue :foo 2, +// 2 => continue :foo 3, +// 3 => return, +// 4 => {}, +// } +// std.debug.print("This statement cannot be reached"); +// } +// +// The flow of execution on this second case is: +// 1. The switch starts with value '1'; +// 2. The switch evaluates to case '1' which in turn uses the continue statement +// to re-evaluate the labeled switch again, now providing the value '2'; +// 3. In the case '2' we repeat the same pattern as case '1' +// but instead the value to be evaluated is now '3'; +// 4. Finally we get to case '3', where we return from the function as a whole. +// +// Since step 4 or a break stament do not exist in this switch, the debug statement is +// never executed +// +const std = @import("std"); + +const PullRequestState = enum(u8) { + Draft, + InReview, + Approved, + Rejected, + Merged, +}; + +pub fn main() void { + // Oh no, your pull request keeps being rejected, + // how would you fix it? + pr: switch (@as(PullRequestState, PullRequestState.Draft)) { + PullRequestState.Draft => continue :pr PullRequestState.InReview, + PullRequestState.InReview => continue :pr PullRequestState.Rejected, + PullRequestState.Approved => continue :pr PullRequestState.Merged, + PullRequestState.Rejected => { + std.debug.print("The pull request has been rejected", .{}); + return; + }, + PullRequestState.Merged => break, // Would you know where to break to? + } + std.debug.print("The pull request has been merged", .{}); +} diff --git a/patches/patches/108_labeled_switch.patch b/patches/patches/108_labeled_switch.patch new file mode 100644 index 0000000..467540c --- /dev/null +++ b/patches/patches/108_labeled_switch.patch @@ -0,0 +1,18 @@ +--- a/exercises/108_labeled_switch.zig ++++ b/exercises/108_labeled_switch.zig +@@ -65,13 +65,13 @@ pub fn main() void { + // how would you fix it? + pr: switch (@as(PullRequestState, PullRequestState.Draft)) { + PullRequestState.Draft => continue :pr PullRequestState.InReview, +- PullRequestState.InReview => continue :pr PullRequestState.Rejected, ++ PullRequestState.InReview => continue :pr PullRequestState.Approved, + PullRequestState.Approved => continue :pr PullRequestState.Merged, + PullRequestState.Rejected => { + std.debug.print("The pull request has been rejected", .{}); + return; + }, +- PullRequestState.Merged => break, // Would you know where to break to? ++ PullRequestState.Merged => break :pr, // Would you know where to break to? + } + std.debug.print("The pull request has been merged", .{}); + } |