Merge pull request 'fixed formatting error' (#496) from format_error into main

Reviewed-on: https://codeberg.org/ziglings/exercises/pulls/496

CONTRIBUTING.md

@@ -95,7 +95,7 @@ interface.  Specifically:
   eternal Ziglings contributor glory is yours!
 
 
-## Licence
+## License
 
 If you submit your contribution to the repository/project,
 you agree that your contribution will be licensed under

build.zig

@@ -81,6 +81,7 @@ pub fn build(b: *Build) !void {
     const run = b.addRunArtifact(elrond);
     run.addArg(b.fmt("--zig={s}", .{b.graph.zig_exe}));
     run.addArg(b.fmt("--work-path={s}", .{work_path}));
+    run.addArg(b.fmt("--root-path={s}", .{b.root.root_dir.path.?}));
 
     if (exno) |n| {
         run.addArg(b.fmt("--only={d}", .{n}));

exercises/005_arrays2.zig

@@ -26,8 +26,13 @@ pub fn main() void {
     // (Problem 2)
     // Please set this array using repetition.
     // It should result in: 1 0 0 1 1 0 0 1 1 0 0 1
-    const bit_pattern_unit = [_]u8{ ??? };
+    const bit_pattern_unit = ???;
-    const bit_pattern: [3 * bit_pattern_unit.len]u8 = @bitCast(@as([3][bit_pattern_unit.len]u8, @splat(bit_pattern_unit)));
+
+    // How long should the bit pattern be?
+    const len = ???;
+
+    // For now, don't worry about the use of SIMD.
+    const bit_pattern: [len]u8 = std.simd.repeat(len, bit_pattern_unit);
 
     // Okay, that's all of the problems. Let's see the results.
     //
@@ -53,3 +58,12 @@ pub fn main() void {
 
     std.debug.print("\n", .{});
 }
+
+// For the curious:
+//
+// The `std.simd.repeat` function takes a target length and a pattern,
+// and returns a vector filled with that pattern repeated to the
+// desired length.
+//
+// For example, `repeat(5, [_]u8{1, 2})` will return a vector
+// equivalent to `.{1, 2, 1, 2, 1}`.

exercises/026_hello2.zig

@@ -30,3 +30,11 @@ pub fn main(init: std.process.Init) !void {
     // We just learned of a single statement which can accomplish this.
     stdout.print("Hello world!\n", .{});
 }
+
+// Now you must be thinking "Why would I need to do this instead of good
+// old 'std.debug.print()'?", but here's what you need to understand:
+// 'std.debug.print()' prints its output to stderr, while the stdout_writer
+// approach prints to stdout.
+// A common practice is to pipe output of a command to other commands,
+// and in order for the piping to work, those commands expect their input
+// to come from stdout, not stderr.

exercises/065_builtins2.zig

@@ -94,7 +94,7 @@ pub fn main() void {
     print("He has room in his heart for:", .{});
 
     // `field_names` is a slice of strings and it holds the names of the struct's fields
-    // `field_types` is a slice of strings and it holds the types of the struct's fields,
+    // `field_types` is a slice of types and it holds the types of the struct's fields,
     //               it is guaranteed to be the same length as `field_names`
     const field_names = @typeInfo(Narcissus).@"struct".field_names;
     const field_types = @typeInfo(Narcissus).@"struct".field_types;

exercises/107_threading.zig

@@ -75,10 +75,10 @@ pub fn main() !void {
     std.debug.print("Starting work...\n", .{});
 
     // These curly braces are very important, they are necessary
-    // to enclose the area where the threads are called.
+    // to enclose the area where the threads are called and joined.
-    // Without these braces, the program would not wait for the
+    // With these braces, the program will block and wait for all threads
-    // end of the threads and they would continue to run beyond the
+    // to finish right at the closing brace of this block, ensuring
-    // end of the program.
+    // "Zig is cool!" is always printed last.
     {
         // Now we start the first thread, with the number as parameter
         const handle = try std.Thread.spawn(.{}, thread_function, .{1});
@@ -102,8 +102,7 @@ pub fn main() !void {
         try io.sleep(std.Io.Duration.fromMilliseconds(400), .awake);
         std.debug.print("Some weird stuff, after starting the threads.\n", .{});
     }
-    // After we have left the closed area, we wait until
+    // The threads are guaranteed to be finished by the time we reach here.
-    // the threads have run through, if this has not yet been the case.
     std.debug.print("Zig is cool!\n", .{});
 }
 

exercises/108_threading2.zig

@@ -28,9 +28,9 @@
 // We will not go into the formula and its derivation in detail, but
 // will deal with the series straight away:
 //
-//        4     4     4     4     4
+//          4     4     4     4     4
-//  PI = --- - --- + --- - --- + --- ...
+//  PI = + --- - --- + --- - --- + --- ...
-//        1     3     5     7     9
+//          1     3     5     7     9
 //
 // As you can clearly see, the series starts with the whole number 4 and
 // approaches the circle number by subtracting and adding smaller and
@@ -71,27 +71,28 @@
 const std = @import("std");
 
 pub fn main() !void {
-    const count = 1_000_000_000;
+    const count = 500_000_000;
+
     var pi_plus: f64 = 0;
     var pi_minus: f64 = 0;
 
     {
         // First thread to calculate the plus numbers.
-        const handle1 = try std.Thread.spawn(.{}, thread_pi, .{ &pi_plus, 5, count });
+        const handle1 = try std.Thread.spawn(.{}, thread_pi, .{ &pi_plus, 1, count });
         defer handle1.join();
 
         // Second thread to calculate the minus numbers.
         ???
-        
     }
+
     // Here we add up the results.
-    std.debug.print("PI ≈ {d:.8}\n", .{4 + pi_plus - pi_minus});
+    std.debug.print("PI ≈ {d:.8} (error = {e:.1})\n", .{ pi_plus - pi_minus, std.math.pi - (pi_plus - pi_minus) });
 }
 
-fn thread_pi(pi: *f64, begin: u64, end: u64) !void {
+fn thread_pi(pi: *f64, begin: u64, count: u64) !void {
-    var n: u64 = begin;
+    for (0..count) |i| {
-    while (n < end) : (n += 4) {
+        const term = 4 / @as(f64, @floatFromInt(begin + 4 * i));
-        pi.* += 4 / @as(f64, @floatFromInt(n));
+        pi.* += term;
     }
 }
 // If you wish, you can increase the number of loop passes, which
@@ -103,8 +104,14 @@ fn thread_pi(pi: *f64, begin: u64, end: u64) !void {
 // is created. Otherwise the debug functions slow down the speed
 // to such an extent that seconds become minutes during execution.
 //
+// You can use the following command to build and run this
+// exercise with the "ReleaseFast" flag:
+//
+//      zig run exercises/108_threading2.zig -O ReleaseFast
+//
 // And you should remove the formatting restriction in "print",
 // otherwise you will not be able to see the additional digits.
 //
-// If count = 10_000_000_000_000 you should see the following:
+// If count = 2_500_000_000_000, you should see the following:
 // 3.141592653589
+// (after waiting on the order of 1000 seconds, or 17 minutes)

exercises/109_files.zig

@@ -50,7 +50,7 @@ pub fn main(init: std.process.Init) !void {
     // wait a minute...
     // opening a directory might fail!
     // what should we do here?
-    var output_dir: std.Io.Dir = try cwd.openDir(io, "output", .{});
+    var output_dir: std.Io.Dir = cwd.openDir(io, "output", .{});
     defer output_dir.close(io);
 
     // we try to open the file `zigling.txt`,

exercises/112_vectors.zig

@@ -145,3 +145,7 @@ pub fn main() void {
     print("Max difference (old fn): {d: >5.3}\n", .{mpd_old});
     print("Max difference (new fn): {d: >5.3}\n", .{mpd_new});
 }
+
+// Another cool feature of Vectors is repeating patterns.
+// Remember the arrays exercise from earlier where we created an array
+// by repeating a pattern? See `005_arrays2.zig`.

patches/patches/005_arrays2.patch

@@ -1,6 +1,6 @@
---- exercises/005_arrays2.zig	2026-05-04 16:26:32.778330847 +0200
+--- exercises/005_arrays2.zig	2026-06-27 09:03:29.918124920 +0000
-+++ answers/005_arrays2.zig	2026-05-04 16:26:13.082917974 +0200
++++ answers/005_arrays2.zig	2026-06-27 09:01:13.162138431 +0000
-@@ -21,12 +21,12 @@
+@@ -21,15 +21,15 @@
      // (Problem 1)
      // Please set this array concatenating the two arrays above.
      // It should result in: 1 3 3 7
@@ -10,8 +10,12 @@
      // (Problem 2)
      // Please set this array using repetition.
      // It should result in: 1 0 0 1 1 0 0 1 1 0 0 1
--    const bit_pattern_unit = [_]u8{ ??? };
+-    const bit_pattern_unit = ???;
 +    const bit_pattern_unit = [_]u8{ 1, 0, 0, 1 };
-     const bit_pattern: [3 * bit_pattern_unit.len]u8 = @bitCast(@as([3][bit_pattern_unit.len]u8, @splat(bit_pattern_unit)));
  
-     // Okay, that's all of the problems. Let's see the results.
+     // How long should the bit pattern be?
+-    const len = ???;
++    const len = 3 * bit_pattern_unit.len;
+ 
+     // For now, don't worry about the use of SIMD.
+     const bit_pattern: [len]u8 = std.simd.repeat(len, bit_pattern_unit);

patches/patches/026_hello2.patch

@@ -1,9 +1,11 @@
---- exercises/026_hello2.zig	2026-01-09 22:51:45.803358789 +0100
+--- exercises/026_hello2.zig	2026-07-01 16:27:18.674459266 +0200
-+++ answers/026_hello2.zig	2026-01-09 22:50:46.016166527 +0100
++++ answers/026_hello2.zig	2026-07-01 16:27:08.579220702 +0200
-@@ -28,5 +28,5 @@
+@@ -28,7 +28,7 @@
      // to be able to pass it up as a return value of main().
      //
      // We just learned of a single statement which can accomplish this.
 -    stdout.print("Hello world!\n", .{});
 +    try stdout.print("Hello world!\n", .{});
  }
+ 
+ // Now you must be thinking "Why would I need to do this instead of good

patches/patches/036_enums2.patch

@@ -1,5 +1,5 @@
---- exercises/036_enums2.zig	2023-10-03 22:15:22.122241138 +0200
+--- exercises/036_enums2.zig	2026-07-21 20:48:50.596099259 +0200
-+++ answers/036_enums2.zig	2023-10-05 20:04:07.002765884 +0200
++++ answers/036_enums2.zig	2026-07-21 20:50:14.726826859 +0200
 @@ -31,7 +31,7 @@
  const Color = enum(u32) {
      red = 0xff0000,
@@ -18,9 +18,11 @@
          \\</p>
          \\
      , .{
-         @intFromEnum(Color.red),
+-        @intFromEnum(Color.red),
-         @intFromEnum(Color.green),
+-        @intFromEnum(Color.green),
 -        @intFromEnum(???), // Oops! We're missing something!
-+        @intFromEnum(Color.blue), // Oops! We're missing something!
++        @backingInt(Color.red),
++        @backingInt(Color.green),
++        @backingInt(Color.blue), // Oops! We're missing something!
      });
  }

patches/patches/108_threading2.patch

@@ -1,13 +1,12 @@
---- exercises/108_threading2.zig	2026-04-14 06:44:18.848246237 +0200
+--- exercises/108_threading2.zig	2026-06-29 23:25:53
-+++ answers/108_threading2.zig	2026-04-14 08:15:30.894485037 +0200
++++ answers/108_threading2.zig	2026-06-29 23:25:25
-@@ -81,8 +81,8 @@
+@@ -82,7 +82,8 @@
          defer handle1.join();
  
          // Second thread to calculate the minus numbers.
 -        ???
--        
 +        const handle2 = try std.Thread.spawn(.{}, thread_pi, .{ &pi_minus, 3, count });
 +        defer handle2.join();
      }
+ 
      // Here we add up the results.
-     std.debug.print("PI ≈ {d:.8}\n", .{4 + pi_plus - pi_minus});

patches/patches/109_files.patch

@@ -1,5 +1,5 @@
---- exercises/109_files.zig	2026-03-20 19:23:48.874150121 +0100
+--- exercises/109_files.zig	2026-06-29 17:08:04.124224900 +0000
-+++ answers/109_files.zig	2026-04-02 10:51:15.813831695 +0200
++++ answers/109_files.zig	2026-06-29 17:13:20.696220533 +0000
 @@ -41,7 +41,7 @@
          // by doing nothing
          //
@@ -9,6 +9,15 @@
          // if there's any other unexpected error we just propagate it through
          else => return e,
      };
+@@ -50,7 +50,7 @@
+     // wait a minute...
+     // opening a directory might fail!
+     // what should we do here?
+-    var output_dir: std.Io.Dir = cwd.openDir(io, "output", .{});
++    var output_dir: std.Io.Dir = try cwd.openDir(io, "output", .{});
+     defer output_dir.close(io);
+ 
+     // we try to open the file `zigling.txt`,
 @@ -61,7 +61,7 @@
      // but here we are not yet done writing to the file
      // if only there were a keyword in Zig that

rivendell/elrond.zig

@@ -19,12 +19,28 @@
 const std = @import("std");
 const builtin = @import("builtin");
 
+const Io = std.Io;
+const File = Io.File;
 const Process = std.process;
+const Terminal = std.Io.Terminal;
 const print = std.debug.print;
 const cutPrefix = std.mem.cutPrefix;
 
 const progress_filename = ".progress.txt";
 
+const no_colors_help =
+    \\Colors are not available.  Check the NO_COLOR environ variable.
+    \\
+    \\
+;
+
+const windows_colors_help =
+    \\Windows colors are not supported.
+    \\Install Windows Terminal or update to a more recent Windows version.
+    \\
+    \\
+;
+
 pub const logo =
     \\         _       _ _
     \\     ___(_) __ _| (_)_ __   __ _ ___
@@ -109,41 +125,23 @@ const Context = struct {
     arena: std.mem.Allocator,
     zig_exe: []const u8,
     work_path: []const u8,
+    root_path: []const u8,
 };
 
 const Error = error{Failed};
 
-// Ansi colors.
+var stderr_term_mode: Terminal.Mode = .no_color;
-var use_color_escapes = false;
-var red_text: []const u8 = "";
-var red_bold_text: []const u8 = "";
-var red_dim_text: []const u8 = "";
-var green_text: []const u8 = "";
-var yellow_text: []const u8 = "";
-var bold_text: []const u8 = "";
-var reset_text: []const u8 = "";
 
-fn setupColors(io: std.Io) void {
+// Ansi colors.
-    use_color_escapes = false;
+const C = struct {
-    const stderr = std.Io.File.stderr();
+    var red: []const u8 = "\x1b[31m";
-    if (stderr.supportsAnsiEscapeCodes(io)) |ok| {
+    var red_bold: []const u8 = "\x1b[31;1m";
-        if (ok) use_color_escapes = true;
+    var red_dim: []const u8 = "\x1b[31;2m";
-    } else |_| {}
+    var green: []const u8 = "\x1b[32m";
-    if (!use_color_escapes and builtin.os.tag == .windows) {
+    var yellow: []const u8 = "\x1b[33m";
-        if (stderr.enableAnsiEscapeCodes(io)) {
+    var bold: []const u8 = "\x1b[1m";
-            use_color_escapes = true;
+    var reset: []const u8 = "\x1b[0m";
-        } else |_| {}
+};
-    }
-    if (use_color_escapes) {
-        red_text = "\x1b[31m";
-        red_bold_text = "\x1b[31;1m";
-        red_dim_text = "\x1b[31;2m";
-        green_text = "\x1b[32m";
-        yellow_text = "\x1b[33m";
-        bold_text = "\x1b[1m";
-        reset_text = "\x1b[0m";
-    }
-}
 
 pub fn main(init: std.process.Init) !void {
     const io = init.io;
@@ -152,24 +150,51 @@ pub fn main(init: std.process.Init) !void {
     var args_it = try init.minimal.args.iterateAllocator(arena);
     if (!args_it.skip()) @panic("expected self arg");
 
-    setupColors(io);
+    const stderr = File.stderr();
+
+    // Setup colors.
+    const NO_COLOR = try init.minimal.environ.containsUnempty(arena, "NO_COLOR");
+    const CLICOLOR_FORCE = try init.minimal.environ.containsUnempty(arena, "CLICOLOR_FORCE");
+
+    const term_mode = try Terminal.Mode.detect(io, stderr, NO_COLOR, CLICOLOR_FORCE);
+    stderr_term_mode = term_mode;
+
+    // Show help in case colors are not available or not supported.
+    switch (term_mode) {
+        .no_color => print(no_colors_help, .{}),
+        .escape_codes => {},
+        .windows_api => print(windows_colors_help, .{}),
+    }
+
+    if (term_mode == .no_color) {
+        C.red = "";
+        C.red_bold = "";
+        C.red_dim = "";
+        C.green = "";
+        C.yellow = "";
+        C.bold = "";
+        C.reset = "";
+    }
 
     if (!validateExercises()) std.process.exit(1);
 
     var zig_exe: []const u8 = "zig";
     var work_path: []const u8 = "exercises";
+    var root_path: []const u8 = "";
     var mode: Mode = .normal;
     var only_n: ?usize = null;
     var start_n: ?usize = null;
 
     while (args_it.next()) |arg| {
         if (std.mem.eql(u8, arg, "--logo")) {
-            print("{s}{s}{s}", .{ yellow_text, logo, reset_text });
+            print("{s}{s}{s}", .{ C.yellow, logo, C.reset });
             return;
         } else if (cutPrefix(u8, arg, "--zig=")) |v| {
             zig_exe = v;
         } else if (cutPrefix(u8, arg, "--work-path=")) |v| {
             work_path = v;
+        } else if (cutPrefix(u8, arg, "--root-path=")) |v| {
+            root_path = v;
         } else if (cutPrefix(u8, arg, "--only=")) |v| {
             only_n = std.fmt.parseInt(usize, v, 10) catch {
                 print("invalid --only value: {s}\n", .{v});
@@ -197,6 +222,7 @@ pub fn main(init: std.process.Init) !void {
         .arena = arena,
         .zig_exe = zig_exe,
         .work_path = work_path,
+        .root_path = root_path,
     };
 
     switch (mode) {
@@ -238,7 +264,7 @@ pub fn main(init: std.process.Init) !void {
                 }
             } else {
                 // All solved.
-                print("{s}All exercises completed!{s}\n", .{ green_text, reset_text });
+                print("{s}All exercises completed!{s}\n", .{ C.green, C.reset });
                 return;
             }
             iterateFrom(ctx, start_index) catch std.process.exit(1);
@@ -260,7 +286,7 @@ fn runOne(ctx: Context, ex: Exercise, mode: Mode) Error!void {
     if (ex.skip) {
         print("Skipping {s}", .{ex.main_file});
         if (ex.skip_hint) |hint|
-            print("\n{s}Reason: {s}{s}\n", .{ bold_text, hint, reset_text });
+            print("\n{s}Reason: {s}{s}\n", .{ C.bold, hint, C.reset });
         print("\n\n", .{});
         return;
     }
@@ -283,7 +309,7 @@ fn runOne(ctx: Context, ex: Exercise, mode: Mode) Error!void {
 
 fn hintAndHelp(ex: Exercise, mode: Mode) void {
     if (ex.hint) |hint|
-        print("\n{s}{s}Ziglings hint: {s}{s}", .{ bold_text, green_text, hint, reset_text });
+        print("\n{s}{s}Ziglings hint: {s}{s}", .{ C.bold, C.green, hint, C.reset });
     help(ex, mode);
 }
 
@@ -310,7 +336,7 @@ fn runExe(ctx: Context, ex: Exercise) !void {
     const arena = ctx.arena;
     print("Compiling {s}...\n", .{ex.main_file});
 
-    const path = std.fs.path.join(arena, &.{ ctx.work_path, ex.main_file }) catch @panic("OOM");
+    const path = std.fs.path.join(arena, &.{ ctx.root_path, ctx.work_path, ex.main_file }) catch @panic("OOM");
 
     var argv = std.ArrayList([]const u8).initCapacity(arena, 8) catch @panic("OOM");
     argv.append(arena, ctx.zig_exe) catch @panic("OOM");
@@ -328,12 +354,11 @@ fn runExe(ctx: Context, ex: Exercise) !void {
         .stderr_limit = .limited(1024 * 1024),
     }) catch |err| {
         print("{s}error:{s} unable to run {s}: {s}\n", .{
-            red_bold_text, reset_text, ex.main_file, @errorName(err),
+            C.red_bold, C.reset, ex.main_file, @errorName(err),
         });
         return err;
     };
 
-    resetLine();
     print("Checking {s}...\n", .{ex.main_file});
 
     return checkOutput(io, arena, ex, result);
@@ -344,8 +369,7 @@ fn runTest(ctx: Context, ex: Exercise) !void {
     const arena = ctx.arena;
     print("Compiling {s}...\n", .{ex.main_file});
 
-    const path = std.fs.path.join(arena, &.{ ctx.work_path, ex.main_file }) catch
+    const path = std.fs.path.join(arena, &.{ ctx.root_path, ctx.work_path, ex.main_file }) catch @panic("OOM");
-        @panic("OOM");
 
     var argv = std.ArrayList([]const u8).initCapacity(arena, 8) catch @panic("OOM");
     argv.append(arena, ctx.zig_exe) catch @panic("OOM");
@@ -362,12 +386,11 @@ fn runTest(ctx: Context, ex: Exercise) !void {
         .stderr_limit = .limited(1024 * 1024),
     }) catch |err| {
         print("{s}error:{s} unable to run test {s}: {s}\n", .{
-            red_bold_text, reset_text, ex.main_file, @errorName(err),
+            C.red_bold, C.reset, ex.main_file, @errorName(err),
         });
         return err;
     };
 
-    resetLine();
     print("Checking {s}...\n", .{ex.main_file});
 
     return checkTest(ex, result);
@@ -384,7 +407,7 @@ fn checkOutput(io: std.Io, arena: std.mem.Allocator, ex: Exercise, result: Proce
         },
         else => {
             print("{s}{s} terminated unexpectedly{s}\n", .{
-                red_bold_text, ex.main_file, reset_text,
+                C.red_bold, ex.main_file, C.reset,
             });
             return Error.Failed;
         },
@@ -419,8 +442,6 @@ fn checkOutput(io: std.Io, arena: std.mem.Allocator, ex: Exercise, result: Proce
     }
 
     if (!std.mem.eql(u8, output, exercise_output)) {
-        const red = red_bold_text;
-        const reset = reset_text;
         print(
             \\
             \\{s}========= expected this output: =========={s}
@@ -428,11 +449,11 @@ fn checkOutput(io: std.Io, arena: std.mem.Allocator, ex: Exercise, result: Proce
             \\{s}========= but found: ====================={s}
             \\{s}
             \\{s}=========================================={s}
-        ++ "\n", .{ red, reset, exercise_output, red, reset, output, red, reset });
+        ++ "\n", .{ C.red_bold, C.reset, exercise_output, C.red_bold, C.reset, output, C.red_bold, C.reset });
         return Error.Failed;
     }
 
-    print("{s}PASSED:\n{s}{s}\n\n", .{ green_text, output, reset_text });
+    print("{s}PASSED:\n{s}{s}\n\n", .{ C.green, output, C.reset });
 }
 
 fn checkTest(ex: Exercise, result: Process.RunResult) !void {
@@ -444,12 +465,12 @@ fn checkTest(ex: Exercise, result: Process.RunResult) !void {
         },
         else => {
             print("{s}{s} terminated unexpectedly{s}\n", .{
-                red_bold_text, ex.main_file, reset_text,
+                C.red_bold, ex.main_file, C.reset,
             });
             return Error.Failed;
         },
     }
-    print("{s}PASSED{s}\n\n", .{ green_text, reset_text });
+    print("{s}PASSED{s}\n\n", .{ C.green, C.reset });
 }
 
 fn help(ex: Exercise, mode: Mode) void {
@@ -459,14 +480,10 @@ fn help(ex: Exercise, mode: Mode) void {
         .random => "zig build -Drandom",
     };
     print("\n{s}Edit exercises/{s} and run '{s}' again.{s}\n", .{
-        red_bold_text, ex.main_file, cmd, reset_text,
+        C.red_bold, ex.main_file, cmd, C.reset,
     });
 }
 
-fn resetLine() void {
-    if (use_color_escapes) print("{s}", .{"\x1b[2K\r"});
-}
-
 // Removes trailing whitespace per line and any trailing LF at the end.
 fn trimLines(arena: std.mem.Allocator, buf: []const u8) ![]const u8 {
     var list = try std.ArrayList(u8).initCapacity(arena, buf.len);
@@ -1150,7 +1167,7 @@ const exercises = [_]Exercise{
     },
     .{
         .main_file = "108_threading2.zig",
-        .output = "PI ≈ 3.14159265",
+        .output = "PI ≈ 3.14159265 (error = 1.0e-9)",
     },
     .{
         .main_file = "109_files.zig",