From 116546a996a12a2e68a68ddf7926d2b4e708c52c Mon Sep 17 00:00:00 2001
From: Arya-Elfren <109028294+Arya-Elfren@users.noreply.github.com>
Date: Wed, 26 Apr 2023 22:07:20 +0100
Subject: [PATCH 01/12] Clarify `f16` maths - closes #204

---
 exercises/060_floats.zig | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/exercises/060_floats.zig b/exercises/060_floats.zig
index 8ba51db..0ebd7a2 100644
--- a/exercises/060_floats.zig
+++ b/exercises/060_floats.zig
@@ -1,7 +1,8 @@
 //
 // Zig has support for IEEE-754 floating-point numbers in these
 // specific sizes: f16, f32, f64, f80, and f128. Floating point
-// literals may be written in scientific notation:
+// literals may be written in the same ways as integers but also
+// in scientific notation:
 //
 //     const a1: f32 = 1200.0;     // 1,200
 //     const a2: f32 = 1.2e+3;     // 1,200
@@ -26,7 +27,10 @@
 // operations with numeric literals, ensure the types match. Zig
 // does not perform unsafe type coercions behind your back:
 //
-//     var foo: f16 = 13.5 * 5;   // ERROR!
+//     fn foo(bar: u16) f16 { return 13.5 * bar; } // ERROR!
+//     var foo: f16 = 13.5 * @as(u8, 5); // ERROR!
+//     var foo: f16 = 13.5 * 5; // This is a safe compile-time
+//                              // conversion, so no problem!
 //     var foo: f16 = 13.5 * 5.0; // No problem, both are floats
 //
 // Please fix the two float problems with this program and

From 18f69f5634c7469042dc601e4c5609af9e0f382c Mon Sep 17 00:00:00 2001
From: Arya-Elfren <109028294+Arya-Elfren@users.noreply.github.com>
Date: Wed, 26 Apr 2023 22:47:03 +0100
Subject: [PATCH 02/12] Clarify the methods syntax sugar & a bit more

I think it's a bit clearer to show exactly what the syntax sugar of methods is, because that's all it is. Every function in Zig is in a struct (files are structs after all) and methods just simplify their use.

I also thought we might use the explicit saturating subtraction as that is why the feature is in Zig.
---
 exercises/047_methods.zig | 43 ++++++++++++++++++++++-----------------
 1 file changed, 24 insertions(+), 19 deletions(-)

diff --git a/exercises/047_methods.zig b/exercises/047_methods.zig
index 96d4c8e..7211caa 100644
--- a/exercises/047_methods.zig
+++ b/exercises/047_methods.zig
@@ -2,9 +2,9 @@
 // Help! Evil alien creatures have hidden eggs all over the Earth
 // and they're starting to hatch!
 //
-// Before you jump into battle, you'll need to know four things:
+// Before you jump into battle, you'll need to know three things:
 //
-// 1. You can attach functions to structs:
+// 1. You can attach functions to structs (and other "type definitions"):
 //
 //     const Foo = struct{
 //         pub fn hello() void {
@@ -12,31 +12,34 @@
 //         }
 //     };
 //
-// 2. A function that is a member of a struct is a "method" and is
-//    called with the "dot syntax" like so:
+// 2. A function that is a member of a struct is "namespaced" within
+//    that struct and is called by specifying the "namespace" and then
+//    using the "dot syntax":
 //
 //     Foo.hello();
 //
-// 3. The NEAT feature of methods is the special parameter named
-//    "self" that takes an instance of that type of struct:
+// 3. The NEAT feature of these functions is that if they take either
+//    an instance of the struct or a pointer to an instance of the struct
+//    then they have some syntax sugar:
 //
 //     const Bar = struct{
-//         number: u32,
-//
-//         pub fn printMe(self: Bar) void {
-//             std.debug.print("{}\n", .{self.number});
-//         }
+//         pub fn a(self: Bar) void { _ = self; }
+//         pub fn b(this: *Bar, other: u8) void { _ = this; _ = other; }
+//         pub fn c(bar: *const Bar) void { _ = bar; }
 //     };
 //
-//    (Actually, you can name the first parameter anything, but
-//    please follow convention and use "self".)
+//    var bar = Bar{};
+//    bar.a() // is equivalent to Bar.a(bar)
+//    bar.b(3) // is equivalent to Bar.b(&bar, 3)
+//    bar.c() // is equivalent to Bar.c(&bar)
 //
-// 4. Now when you call the method on an INSTANCE of that struct
-//    with the "dot syntax", the instance will be automatically
-//    passed as the "self" parameter:
+//    Notice that the name of the parameter doesn't matter. Some use
+//    self, others use a lowercase version of the type name, but feel
+//    free to use whatever is most appropriate.
 //
-//     var my_bar = Bar{ .number = 2000 };
-//     my_bar.printMe(); // prints "2000"
+//    Effectively, the method syntax sugar just does this transformation:
+//        thing.function(args);
+//        @TypeOf(thing).function(thing, args);
 //
 // Okay, you're armed.
 //
@@ -63,7 +66,9 @@ const HeatRay = struct {
 
     // We love this method:
     pub fn zap(self: HeatRay, alien: *Alien) void {
-        alien.health -= if (self.damage >= alien.health) alien.health else self.damage;
+        alien.health -|= self.damage; // Saturating inplace substraction
+                                      // It subtracts but doesn't go below the
+                                      // lowest value for our type (in this case 0)
     }
 };
 

From 3612c67f04e0d902a12c3f71ed52b1de8422804e Mon Sep 17 00:00:00 2001
From: Arya-Elfren <109028294+Arya-Elfren@users.noreply.github.com>
Date: Fri, 28 Apr 2023 11:12:42 +0100
Subject: [PATCH 03/12] Simplify methods explanation in 047

---
 exercises/047_methods.zig | 20 +++++++-------------
 1 file changed, 7 insertions(+), 13 deletions(-)

diff --git a/exercises/047_methods.zig b/exercises/047_methods.zig
index 7211caa..6b2dbef 100644
--- a/exercises/047_methods.zig
+++ b/exercises/047_methods.zig
@@ -18,14 +18,14 @@
 //
 //     Foo.hello();
 //
-// 3. The NEAT feature of these functions is that if they take either
-//    an instance of the struct or a pointer to an instance of the struct
-//    then they have some syntax sugar:
+// 3. The NEAT feature of these functions is that if their first argument
+//    is an instance of the struct (or a pointer to one) then we can use
+//    the instance as the namespace instead of the type:
 //
 //     const Bar = struct{
-//         pub fn a(self: Bar) void { _ = self; }
-//         pub fn b(this: *Bar, other: u8) void { _ = this; _ = other; }
-//         pub fn c(bar: *const Bar) void { _ = bar; }
+//         pub fn a(self: Bar) void {}
+//         pub fn b(this: *Bar, other: u8) void {}
+//         pub fn c(bar: *const Bar) void {}
 //     };
 //
 //    var bar = Bar{};
@@ -37,10 +37,6 @@
 //    self, others use a lowercase version of the type name, but feel
 //    free to use whatever is most appropriate.
 //
-//    Effectively, the method syntax sugar just does this transformation:
-//        thing.function(args);
-//        @TypeOf(thing).function(thing, args);
-//
 // Okay, you're armed.
 //
 // Now, please zap the alien structs until they're all gone or
@@ -66,9 +62,7 @@ const HeatRay = struct {
 
     // We love this method:
     pub fn zap(self: HeatRay, alien: *Alien) void {
-        alien.health -|= self.damage; // Saturating inplace substraction
-                                      // It subtracts but doesn't go below the
-                                      // lowest value for our type (in this case 0)
+        alien.health -= if (self.damage >= alien.health) alien.health else self.damage;
     }
 };
 

From 599bea57051efcfaa7a81cb2a846fe095b9759c0 Mon Sep 17 00:00:00 2001
From: Arya-Elfren <109028294+Arya-Elfren@users.noreply.github.com>
Date: Fri, 28 Apr 2023 11:32:45 +0100
Subject: [PATCH 04/12] Simplify `f16` coersion example

---
 exercises/060_floats.zig | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/exercises/060_floats.zig b/exercises/060_floats.zig
index 0ebd7a2..a04a54d 100644
--- a/exercises/060_floats.zig
+++ b/exercises/060_floats.zig
@@ -23,15 +23,12 @@
 //     const pi: f16 = 3.1415926535;   // rounds to 3.140625
 //     const av: f16 = 6.02214076e+23; // Avogadro's inf(inity)!
 //
-// A float literal has a decimal point. When performing math
+// A float literal doesn't need a decimal point. When performing math
 // operations with numeric literals, ensure the types match. Zig
 // does not perform unsafe type coercions behind your back:
 //
-//     fn foo(bar: u16) f16 { return 13.5 * bar; } // ERROR!
-//     var foo: f16 = 13.5 * @as(u8, 5); // ERROR!
-//     var foo: f16 = 13.5 * 5; // This is a safe compile-time
-//                              // conversion, so no problem!
-//     var foo: f16 = 13.5 * 5.0; // No problem, both are floats
+//    var foo: f16 = 5; // NO ERROR
+//    var foo: f16 = @as(u16, 5); // ERROR
 //
 // Please fix the two float problems with this program and
 // display the result as a whole number.

From c2fe843a8a780e77e9875c9f6da8b3c3999915f2 Mon Sep 17 00:00:00 2001
From: Arya-Elfren <109028294+Arya-Elfren@users.noreply.github.com>
Date: Fri, 28 Apr 2023 15:11:43 +0100
Subject: [PATCH 05/12] 060 - remove `@as()`

---
 exercises/060_floats.zig | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/exercises/060_floats.zig b/exercises/060_floats.zig
index a04a54d..1320171 100644
--- a/exercises/060_floats.zig
+++ b/exercises/060_floats.zig
@@ -4,8 +4,8 @@
 // literals may be written in the same ways as integers but also
 // in scientific notation:
 //
-//     const a1: f32 = 1200.0;     // 1,200
-//     const a2: f32 = 1.2e+3;     // 1,200
+//     const a1: f32 = 1200;       //    1,200
+//     const a2: f32 = 1.2e+3;     //    1,200
 //     const b1: f32 = -500_000.0; // -500,000
 //     const b2: f32 = -5.0e+5;    // -500,000
 //
@@ -23,12 +23,14 @@
 //     const pi: f16 = 3.1415926535;   // rounds to 3.140625
 //     const av: f16 = 6.02214076e+23; // Avogadro's inf(inity)!
 //
-// A float literal doesn't need a decimal point. When performing math
-// operations with numeric literals, ensure the types match. Zig
-// does not perform unsafe type coercions behind your back:
+// When performing math operations with numeric literals, ensure
+// the types match. Zig does not perform unsafe type coercions
+// behind your back:
 //
 //    var foo: f16 = 5; // NO ERROR
-//    var foo: f16 = @as(u16, 5); // ERROR
+//
+//    var foo: u16 = 5; // A literal of a different type
+//    var bar: f16 = foo; // ERROR
 //
 // Please fix the two float problems with this program and
 // display the result as a whole number.

From 5c488a1402be83f198cc29f23f448313001a9a1c Mon Sep 17 00:00:00 2001
From: Manlio Perillo <manlio.perillo@gmail.com>
Date: Thu, 4 May 2023 16:34:17 +0200
Subject: [PATCH 06/12] test: improve test case 1 and 2

In test case 1 and 2, remove the `i` variable and use `ex.number()`
instead.

In test case 2, when checking the exercise output from stderr, also
check that stdout is empty and vice versa.
---
 test/tests.zig | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/test/tests.zig b/test/tests.zig
index 752ca50..060b553 100644
--- a/test/tests.zig
+++ b/test/tests.zig
@@ -32,21 +32,23 @@ pub fn addCliTests(b: *std.Build, exercises: []const Exercise) *Step {
         // Test that `zig build -Dhealed -Dn=n test` selects the nth exercise.
         const case_step = createCase(b, "case-1");
 
-        var i: usize = 0;
         for (exercises[0 .. exercises.len - 1]) |ex| {
-            i += 1;
+            const n = ex.number();
             if (ex.skip) continue;
 
             const cmd = b.addSystemCommand(
-                &.{ b.zig_exe, "build", "-Dhealed", b.fmt("-Dn={}", .{i}), "test" },
+                &.{ b.zig_exe, "build", "-Dhealed", b.fmt("-Dn={}", .{n}), "test" },
             );
-            cmd.setName(b.fmt("zig build -Dhealed -Dn={} test", .{i}));
+            cmd.setName(b.fmt("zig build -Dhealed -Dn={} test", .{n}));
             cmd.expectExitCode(0);
 
-            if (ex.check_stdout)
-                expectStdOutMatch(cmd, ex.output)
-            else
+            if (ex.check_stdout) {
+                expectStdOutMatch(cmd, ex.output);
+                cmd.expectStdErrEqual("");
+            } else {
                 expectStdErrMatch(cmd, ex.output);
+                cmd.expectStdOutEqual("");
+            }
 
             cmd.step.dependOn(&heal_step.step);
 
@@ -60,15 +62,14 @@ pub fn addCliTests(b: *std.Build, exercises: []const Exercise) *Step {
         // Test that `zig build -Dhealed -Dn=n test` skips disabled esercises.
         const case_step = createCase(b, "case-2");
 
-        var i: usize = 0;
         for (exercises[0 .. exercises.len - 1]) |ex| {
-            i += 1;
+            const n = ex.number();
             if (!ex.skip) continue;
 
             const cmd = b.addSystemCommand(
-                &.{ b.zig_exe, "build", "-Dhealed", b.fmt("-Dn={}", .{i}), "test" },
+                &.{ b.zig_exe, "build", "-Dhealed", b.fmt("-Dn={}", .{n}), "test" },
             );
-            cmd.setName(b.fmt("zig build -Dhealed -Dn={} test", .{i}));
+            cmd.setName(b.fmt("zig build -Dhealed -Dn={} test", .{n}));
             cmd.expectExitCode(0);
             cmd.expectStdOutEqual("");
             expectStdErrMatch(cmd, b.fmt("{s} skipped", .{ex.main_file}));

From 277c95db7af09732f5179677fcbd191e36fefc81 Mon Sep 17 00:00:00 2001
From: Manlio Perillo <manlio.perillo@gmail.com>
Date: Thu, 4 May 2023 18:48:35 +0200
Subject: [PATCH 07/12] test: fix doc-comments

CheckStep, FailStep, fail, HealStep and heal incorrectly used a normal
comment, instead of a doc-comment.

Additionally, improve the documentation for FailStep and HealStep.
---
 test/tests.zig | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/test/tests.zig b/test/tests.zig
index 060b553..dbf237b 100644
--- a/test/tests.zig
+++ b/test/tests.zig
@@ -158,7 +158,7 @@ fn createCase(b: *Build, name: []const u8) *Step {
     return case_step;
 }
 
-// Check the output of `zig build` or `zig build -Dn=1 start`.
+/// Checks the output of `zig build` or `zig build -Dn=1 start`.
 const CheckStep = struct {
     step: Step,
     exercises: []const Exercise,
@@ -282,7 +282,7 @@ const CheckStep = struct {
     }
 };
 
-// A step that will fail.
+/// Fails with a custom error message.
 const FailStep = struct {
     step: Step,
     error_msg: []const u8,
@@ -311,9 +311,9 @@ const FailStep = struct {
     }
 };
 
-// A variant of `std.Build.Step.fail` that does not return an error so that it
-// can be used in the configuration phase.  It returns a FailStep, so that the
-// error will be cleanly handled by the build runner.
+/// A variant of `std.Build.Step.fail` that does not return an error so that it
+/// can be used in the configuration phase.  It returns a FailStep, so that the
+/// error will be cleanly handled by the build runner.
 fn fail(step: *Step, comptime format: []const u8, args: anytype) *Step {
     const b = step.owner;
 
@@ -323,7 +323,7 @@ fn fail(step: *Step, comptime format: []const u8, args: anytype) *Step {
     return step;
 }
 
-// A step that heals exercises.
+/// Heals the exercises.
 const HealStep = struct {
     step: Step,
     exercises: []const Exercise,
@@ -353,7 +353,7 @@ const HealStep = struct {
     }
 };
 
-// Heals all the exercises.
+/// Heals all the exercises.
 fn heal(allocator: Allocator, exercises: []const Exercise, work_path: []const u8) !void {
     const join = fs.path.join;
 

From eda73b2fa8dcb5ca4fc96903f8d1f46ac464acab Mon Sep 17 00:00:00 2001
From: Manlio Perillo <manlio.perillo@gmail.com>
Date: Thu, 4 May 2023 19:01:48 +0200
Subject: [PATCH 08/12] test: remove obsolete comment in the heal function

Remove the comment about using POSIX patch variant, since we now use the
-s option.
---
 test/tests.zig | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/test/tests.zig b/test/tests.zig
index dbf237b..1fda49d 100644
--- a/test/tests.zig
+++ b/test/tests.zig
@@ -7,6 +7,7 @@ const fs = std.fs;
 const mem = std.mem;
 
 const Allocator = std.mem.Allocator;
+const Child = std.process.Child;
 const Build = std.build;
 const FileSource = std.Build.FileSource;
 const Reader = fs.File.Reader;
@@ -363,7 +364,6 @@ fn heal(allocator: Allocator, exercises: []const Exercise, work_path: []const u8
     for (exercises) |ex| {
         const name = ex.name();
 
-        // Use the POSIX patch variant.
         const file = try join(allocator, &.{ exercises_path, ex.main_file });
         const patch = b: {
             const patch_name = try fmt.allocPrint(allocator, "{s}.patch", .{name});
@@ -373,7 +373,7 @@ fn heal(allocator: Allocator, exercises: []const Exercise, work_path: []const u8
 
         const argv = &.{ "patch", "-i", patch, "-o", output, "-s", file };
 
-        var child = std.process.Child.init(argv, allocator);
+        var child = Child.init(argv, allocator);
         _ = try child.spawnAndWait();
     }
 }

From 8a3d722a33ed09fd8e534fffa0bb67d84f40528a Mon Sep 17 00:00:00 2001
From: Dave Gauer <dave@ratfactor.com>
Date: Thu, 4 May 2023 19:04:58 -0400
Subject: [PATCH 09/12] Ex 001 remove ancient script reference + wording

---
 exercises/001_hello.zig | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/exercises/001_hello.zig b/exercises/001_hello.zig
index d2093c7..9534b60 100644
--- a/exercises/001_hello.zig
+++ b/exercises/001_hello.zig
@@ -1,18 +1,18 @@
 //
-// Oh no! This program is supposed to print "Hello world!" but it needs
-// your help!
+// Oh no, this is supposed to print "Hello world!" but it needs
+// your help.
 //
+// Zig functions are private by default but the main() function
+// should be public.
 //
-// Zig functions are private by default but the main() function should
-// be public.
-//
-// A function is declared public with the "pub" statement like so:
+// A function is made public with the "pub" statement like so:
 //
 //     pub fn foo() void {
 //         ...
 //     }
 //
-// Try to fix the program and run `ziglings` to see if it works!
+// Perhaps knowing this well help solve the errors we're getting
+// with this little program?
 //
 const std = @import("std");
 

From 25611b831255cd1a84b837c708a7e6398d133869 Mon Sep 17 00:00:00 2001
From: Arnon <98772127+arnon4@users.noreply.github.com>
Date: Fri, 5 May 2023 13:11:20 +0300
Subject: [PATCH 10/12] Fixed example syntax for inline else

---
 exercises/092_interfaces.zig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/exercises/092_interfaces.zig b/exercises/092_interfaces.zig
index 5ac5768..8f0a937 100644
--- a/exercises/092_interfaces.zig
+++ b/exercises/092_interfaces.zig
@@ -40,7 +40,7 @@
 //
 //   switch (thing) {
 //       .a => |a| special(a),
-//       inline else |t| => normal(t),
+//       inline else => |t| normal(t),
 //   }
 //
 // We can have special handling of some cases and then Zig

From 0cd86d2f9b8a372c7c8ab2a253e3643cc2ab6212 Mon Sep 17 00:00:00 2001
From: Manlio Perillo <manlio.perillo@gmail.com>
Date: Fri, 5 May 2023 16:13:57 +0200
Subject: [PATCH 11/12] build: add the healed-path option

This is necessary in the unit tests, to ensure each test case use a
different exercises directory.

Update test/tests.zig to use the new healed-path option, ensuring that
each temp directory is removed.

In test case 3, 4 and 5, move case_step as the first step in the
dependency chain.  This will improve the build summary tree.

In test case 5, remove the dependency to heal_step, since it is not
necessary.
---
 build.zig      |   9 ++--
 test/tests.zig | 119 ++++++++++++++++++++++++++++++++++---------------
 2 files changed, 89 insertions(+), 39 deletions(-)

diff --git a/build.zig b/build.zig
index 64968b9..a880450 100644
--- a/build.zig
+++ b/build.zig
@@ -118,11 +118,12 @@ pub fn build(b: *Build) !void {
         \\
     ;
 
-    const use_healed = b.option(bool, "healed", "Run exercises from patches/healed") orelse false;
+    const healed = b.option(bool, "healed", "Run exercises from patches/healed") orelse false;
+    const override_healed_path = b.option([]const u8, "healed-path", "Override healed path");
     const exno: ?usize = b.option(usize, "n", "Select exercise");
 
-    const healed_path = "patches/healed";
-    const work_path = if (use_healed) healed_path else "exercises";
+    const healed_path = if (override_healed_path) |path| path else "patches/healed";
+    const work_path = if (healed) healed_path else "exercises";
 
     const header_step = PrintStep.create(b, logo);
 
@@ -168,7 +169,7 @@ pub fn build(b: *Build) !void {
         start_step.dependOn(&prev_step.step);
 
         return;
-    } else if (use_healed and false) {
+    } else if (healed and false) {
         // Special case when healed by the eowyn script, where we can make the
         // code more efficient.
         //
diff --git a/test/tests.zig b/test/tests.zig
index 1fda49d..0fd3286 100644
--- a/test/tests.zig
+++ b/test/tests.zig
@@ -19,27 +19,28 @@ const Exercise = root.Exercise;
 pub fn addCliTests(b: *std.Build, exercises: []const Exercise) *Step {
     const step = b.step("test-cli", "Test the command line interface");
 
-    // We should use a temporary path, but it will make the implementation of
-    // `build.zig` more complex.
-    const work_path = "patches/healed";
-
-    fs.cwd().makePath(work_path) catch |err| {
-        return fail(step, "unable to make '{s}': {s}\n", .{ work_path, @errorName(err) });
-    };
-
-    const heal_step = HealStep.create(b, exercises, work_path);
-
     {
         // Test that `zig build -Dhealed -Dn=n test` selects the nth exercise.
         const case_step = createCase(b, "case-1");
 
+        const tmp_path = makeTempPath(b) catch |err| {
+            return fail(step, "unable to make tmp path: {s}\n", .{@errorName(err)});
+        };
+
+        const heal_step = HealStep.create(b, exercises, tmp_path);
+
         for (exercises[0 .. exercises.len - 1]) |ex| {
             const n = ex.number();
             if (ex.skip) continue;
 
-            const cmd = b.addSystemCommand(
-                &.{ b.zig_exe, "build", "-Dhealed", b.fmt("-Dn={}", .{n}), "test" },
-            );
+            const cmd = b.addSystemCommand(&.{
+                b.zig_exe,
+                "build",
+                "-Dhealed",
+                b.fmt("-Dhealed-path={s}", .{tmp_path}),
+                b.fmt("-Dn={}", .{n}),
+                "test",
+            });
             cmd.setName(b.fmt("zig build -Dhealed -Dn={} test", .{n}));
             cmd.expectExitCode(0);
 
@@ -56,20 +57,34 @@ pub fn addCliTests(b: *std.Build, exercises: []const Exercise) *Step {
             case_step.dependOn(&cmd.step);
         }
 
-        step.dependOn(case_step);
+        const cleanup = b.addRemoveDirTree(tmp_path);
+        cleanup.step.dependOn(case_step);
+
+        step.dependOn(&cleanup.step);
     }
 
     {
         // Test that `zig build -Dhealed -Dn=n test` skips disabled esercises.
         const case_step = createCase(b, "case-2");
 
+        const tmp_path = makeTempPath(b) catch |err| {
+            return fail(step, "unable to make tmp path: {s}\n", .{@errorName(err)});
+        };
+
+        const heal_step = HealStep.create(b, exercises, tmp_path);
+
         for (exercises[0 .. exercises.len - 1]) |ex| {
             const n = ex.number();
             if (!ex.skip) continue;
 
-            const cmd = b.addSystemCommand(
-                &.{ b.zig_exe, "build", "-Dhealed", b.fmt("-Dn={}", .{n}), "test" },
-            );
+            const cmd = b.addSystemCommand(&.{
+                b.zig_exe,
+                "build",
+                "-Dhealed",
+                b.fmt("-Dhealed-path={s}", .{tmp_path}),
+                b.fmt("-Dn={}", .{n}),
+                "test",
+            });
             cmd.setName(b.fmt("zig build -Dhealed -Dn={} test", .{n}));
             cmd.expectExitCode(0);
             cmd.expectStdOutEqual("");
@@ -80,15 +95,30 @@ pub fn addCliTests(b: *std.Build, exercises: []const Exercise) *Step {
             case_step.dependOn(&cmd.step);
         }
 
-        step.dependOn(case_step);
+        const cleanup = b.addRemoveDirTree(tmp_path);
+        cleanup.step.dependOn(case_step);
+
+        step.dependOn(&cleanup.step);
     }
 
     {
         // Test that `zig build -Dhealed` process all the exercises in order.
         const case_step = createCase(b, "case-3");
 
+        const tmp_path = makeTempPath(b) catch |err| {
+            return fail(step, "unable to make tmp path: {s}\n", .{@errorName(err)});
+        };
+
+        const heal_step = HealStep.create(b, exercises, tmp_path);
+        heal_step.step.dependOn(case_step);
+
         // TODO: when an exercise is modified, the cache is not invalidated.
-        const cmd = b.addSystemCommand(&.{ b.zig_exe, "build", "-Dhealed" });
+        const cmd = b.addSystemCommand(&.{
+            b.zig_exe,
+            "build",
+            "-Dhealed",
+            b.fmt("-Dhealed-path={s}", .{tmp_path}),
+        });
         cmd.setName("zig build -Dhealed");
         cmd.expectExitCode(0);
         cmd.step.dependOn(&heal_step.step);
@@ -97,9 +127,10 @@ pub fn addCliTests(b: *std.Build, exercises: []const Exercise) *Step {
         const verify = CheckStep.create(b, exercises, stderr, true);
         verify.step.dependOn(&cmd.step);
 
-        case_step.dependOn(&verify.step);
+        const cleanup = b.addRemoveDirTree(tmp_path);
+        cleanup.step.dependOn(&verify.step);
 
-        step.dependOn(case_step);
+        step.dependOn(&cleanup.step);
     }
 
     {
@@ -107,10 +138,22 @@ pub fn addCliTests(b: *std.Build, exercises: []const Exercise) *Step {
         // in order.
         const case_step = createCase(b, "case-4");
 
+        const tmp_path = makeTempPath(b) catch |err| {
+            return fail(step, "unable to make tmp path: {s}\n", .{@errorName(err)});
+        };
+
+        const heal_step = HealStep.create(b, exercises, tmp_path);
+        heal_step.step.dependOn(case_step);
+
         // TODO: when an exercise is modified, the cache is not invalidated.
-        const cmd = b.addSystemCommand(
-            &.{ b.zig_exe, "build", "-Dhealed", "-Dn=1", "start" },
-        );
+        const cmd = b.addSystemCommand(&.{
+            b.zig_exe,
+            "build",
+            "-Dhealed",
+            b.fmt("-Dhealed-path={s}", .{tmp_path}),
+            "-Dn=1",
+            "start",
+        });
         cmd.setName("zig build -Dhealed -Dn=1 start");
         cmd.expectExitCode(0);
         cmd.step.dependOn(&heal_step.step);
@@ -119,9 +162,10 @@ pub fn addCliTests(b: *std.Build, exercises: []const Exercise) *Step {
         const verify = CheckStep.create(b, exercises, stderr, false);
         verify.step.dependOn(&cmd.step);
 
-        case_step.dependOn(&verify.step);
+        const cleanup = b.addRemoveDirTree(tmp_path);
+        cleanup.step.dependOn(&verify.step);
 
-        step.dependOn(case_step);
+        step.dependOn(&cleanup.step);
     }
 
     {
@@ -133,18 +177,11 @@ pub fn addCliTests(b: *std.Build, exercises: []const Exercise) *Step {
         cmd.expectExitCode(1);
         expectStdErrMatch(cmd, exercises[0].hint);
 
-        cmd.step.dependOn(&heal_step.step);
-
-        case_step.dependOn(&cmd.step);
+        cmd.step.dependOn(case_step);
 
-        step.dependOn(case_step);
+        step.dependOn(&cmd.step);
     }
 
-    // Don't add the cleanup step, since it may delete work_path while a test
-    // case is running.
-    //const cleanup = b.addRemoveDirTree(work_path);
-    //step.dependOn(&cleanup.step);
-
     return step;
 }
 
@@ -378,6 +415,18 @@ fn heal(allocator: Allocator, exercises: []const Exercise, work_path: []const u8
     }
 }
 
+/// This function is the same as the one in std.Build.makeTempPath, with the
+/// difference that returns an error when the temp path cannot be created.
+pub fn makeTempPath(b: *Build) ![]const u8 {
+    const rand_int = std.crypto.random.int(u64);
+    const tmp_dir_sub_path = "tmp" ++ fs.path.sep_str ++ Build.hex64(rand_int);
+    const path = b.cache_root.join(b.allocator, &.{tmp_dir_sub_path}) catch
+        @panic("OOM");
+    try b.cache_root.handle.makePath(tmp_dir_sub_path);
+
+    return path;
+}
+
 //
 // Missing functions from std.Build.RunStep
 //

From e5341b91c107894e585e515731d5ec34fd56c1af Mon Sep 17 00:00:00 2001
From: Dave Gauer <dave@ratfactor.com>
Date: Fri, 5 May 2023 18:34:36 -0400
Subject: [PATCH 12/12] Ex 101: Magic bags better than buckets for metaphors

---
 exercises/101_for5.zig | 32 +++++++++++++++++---------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/exercises/101_for5.zig b/exercises/101_for5.zig
index 3861417..037989f 100644
--- a/exercises/101_for5.zig
+++ b/exercises/101_for5.zig
@@ -79,19 +79,19 @@ pub fn main() void {
 // all about:
 //
 // Let's say you've been tasked with grabbing three glass
-// marbles, three spoons, and three feathers from a bucket. But
-// you can't use your hands to grab them. Instead, you have a
-// special marble scoop, spoon magnet, and feather tongs to grab
+// marbles, three spoons, and three feathers from a magic bag.
+// But you can't use your hands to grab them. Instead, you must
+// use a marble scoop, spoon magnet, and feather tongs to grab
 // each type of object.
 //
-// Now, would you rather have:
+// Now, would you rather the magic bag:
 //
-// A. The items layered so you have to pick up one marble, then
-//    one spoon, then one feather?
+// A. Grouped the items in clusters so you have to pick up one
+//    marble, then one spoon, then one feather?
 //
 //    OR
 //
-// B. The items separated by type so you can pick up all of the
+// B. Grouped the items by type so you can pick up all of the
 //    marbles at once, then all the spoons, then all of the
 //    feathers?
 //
@@ -103,14 +103,16 @@ pub fn main() void {
 // efficient for modern CPUs.
 //
 // Decades of OOP practices have steered people towards grouping
-// different data types together into "objects" with the hope
-// that it would be friendlier to the human mind. But
-// data-oriented design groups data in a way that is more
-// efficient for the computer.
-//
-// In Zig terminology, the difference in groupings is sometimes
-// known as "Array of Structs" (AoS) versus "Struct of Arrays"
-// (SoA).
+// different data types together into mixed-type "objects" with
+// the intent that these are easier on the human mind.
+// Data-oriented design groups data by type in a way that is
+// easier on the computer.
+//
+// With clever language design, maybe we can have both.
+//
+// In the Zig community, you may see the difference in groupings
+// presented with the terms "Array of Structs" (AoS) versus
+// "Struct of Arrays" (SoA).
 //
 // To envision these two designs in action, imagine an array of
 // RPG character structs, each containing three different data