099-105 completed

exercises/099_formatting.zig

@@ -131,7 +131,7 @@ pub fn main() !void {
         for (0..size) |b| {
             // What formatting is needed here to make our columns
             // nice and straight?
-            print("{???} ", .{(a + 1) * (b + 1)});
+            print("{d:>3} ", .{(a + 1) * (b + 1)});
         }
 
         // After each row we use double line feed:

exercises/100_for4.zig

@@ -39,7 +39,7 @@ pub fn main() void {
     const hex_nums = [_]u8{ 0xb, 0x2a, 0x77 };
     const dec_nums = [_]u8{ 11, 42, 119 };
 
-    for (hex_nums, ???) |hn, ???| {
+    for (hex_nums, dec_nums) |hn, dn| {
         if (hn != dn) {
             std.debug.print("Uh oh! Found a mismatch: {d} vs {d}\n", .{ hn, dn });
             return;

exercises/101_for5.zig

@@ -51,7 +51,7 @@ pub fn main() void {
 
     // We would like to number our list starting with 1, not 0.
     // How do we do that?
-    for (roles, gold, experience, ???) |c, g, e, i| {
+    for (roles, gold, experience, 1..) |c, g, e, i| {
         const role_name = switch (c) {
             .wizard => "Wizard",
             .thief => "Thief",

exercises/102_testing.zig

@@ -83,7 +83,7 @@ fn sub(a: f16, b: f16) f16 {
 // an error that you need
 // to correct.
 test "sub" {
-    try testing.expect(sub(10, 5) == 6);
+    try testing.expect(sub(10, 5) == 5);
 
     try testing.expect(sub(3, 1.5) == 1.5);
 }
@@ -108,5 +108,5 @@ test "divide" {
     // Now we test if the function returns an error
     // if we pass a zero as denominator.
     // But which error needs to be tested?
-    try testing.expectError(error.???, divide(15, 0));
+    try testing.expectError(error.DivisionByZero, divide(15, 0));
 }

exercises/103_tokenization.zig

@@ -119,9 +119,9 @@
 // after all we need some practice. Suppose we want to count the words
 // of this little poem:
 //
-// 	My name is Ozymandias, King of Kings;
-// 	Look on my Works, ye Mighty, and despair!
-// 	 by Percy Bysshe Shelley
+//  My name is Ozymandias, King of Kings;
+//  Look on my Works, ye Mighty, and despair!
+//   by Percy Bysshe Shelley
 //
 //
 const std = @import("std");
@@ -136,7 +136,7 @@ pub fn main() !void {
     ;
 
     // now the tokenizer, but what do we need here?
-    var it = std.mem.tokenizeAny(u8, poem, ???);
+    var it = std.mem.tokenizeAny(u8, poem, " ,;!\n");
 
     // print all words and count them
     var cnt: usize = 0;

exercises/104_threading.zig

@@ -97,12 +97,12 @@ pub fn main() !void {
         defer handle.join();
 
         // Second thread
-        const handle2 = try std.Thread.spawn(.{}, thread_function, .{-4}); // that can't be right?
+        const handle2 = try std.Thread.spawn(.{}, thread_function, .{2}); // that can't be right?
         defer handle2.join();
 
         // Third thread
         const handle3 = try std.Thread.spawn(.{}, thread_function, .{3});
-        defer ??? // <-- something is missing
+        defer handle3.join(); // <-- something is missing
 
         // After the threads have been started,
         // they run in parallel and we can still do some work in between.

exercises/105_threading2.zig

@@ -81,8 +81,8 @@ pub fn main() !void {
         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});