Merge pull request 'Add another defer exercise' (#438) from mark2185/exercises:defer3 into main

Reviewed-on: https://codeberg.org/ziglings/exercises/pulls/438

exercises/028_defer2.zig

@@ -10,6 +10,8 @@ pub fn main() void {
     for (animals) |a| printAnimal(a);
 
     std.debug.print("done.\n", .{});
+
+    std.debug.print("Answer to everything? {d}\n", .{calculateTheUltimateQuestionOfLife()});
 }
 
 // This function is _supposed_ to print an animal name in parentheses
@@ -35,3 +37,24 @@ fn printAnimal(animal: u8) void {
 
     std.debug.print("Unknown", .{});
 }
+
+// This function is supposed to calculate the answer to the
+// ultimate question of life, the universe, and everything,
+// but it needs to be deferred as far in the future as possible,
+// in order to gather more data.
+//
+// When there are multiple defers in a single block, they are executed in reverse order.
+// This example might seem silly, but it's important to know when e.g.
+// deinitializing containers whose elements need to be deinitialized first.
+fn calculateTheUltimateQuestionOfLife() u32 {
+    var x: u32 = 100;
+
+    // Try reordering the statements to get the answer 42
+    {
+        defer x = x / 10;
+        defer x = x + 11;
+        defer x = x * 2;
+    }
+
+    return x;
+}

patches/patches/028_defer2.patch

@@ -1,6 +1,6 @@
---- exercises/028_defer2.zig	2023-10-03 22:15:22.122241138 +0200
+--- exercises/028_defer2.zig	2026-06-02 06:08:12.713672612 +0200
-+++ answers/028_defer2.zig	2023-10-05 20:04:06.966098530 +0200
++++ answers/028_defer2.zig	2026-06-02 06:08:43.262234023 +0200
-@@ -18,7 +18,7 @@
+@@ -20,7 +20,7 @@
  fn printAnimal(animal: u8) void {
      std.debug.print("(", .{});
  
@@ -9,3 +9,15 @@
  
      if (animal == 'g') {
          std.debug.print("Goat", .{});
+@@ -51,9 +51,9 @@
+ 
+     // Try reordering the statements to get the answer 42
+     {
+-        defer x = x / 10;
+-        defer x = x + 11;
+         defer x = x * 2;
++        defer x = x + 11;
++        defer x = x / 10;
+     }
+ 
+     return x;

src/elrond.zig

@@ -693,7 +693,10 @@ const exercises = [_]Exercise{
     },
     .{
         .main_file = "028_defer2.zig",
-        .output = "(Goat) (Cat) (Dog) (Dog) (Goat) (Unknown) done.",
+        .output =
+        \\(Goat) (Cat) (Dog) (Dog) (Goat) (Unknown) done.
+        \\Answer to everything? 42
+        , // pay attention to the comma
     },
     .{
         .main_file = "029_errdefer.zig",