Finished quiz 4 - dealing with errors

Reviewed-on: https://codeberg.org/ziglings/exercises/pulls/198

exercises/001_hello.zig

@@ -16,6 +16,6 @@
 //
 const std = @import("std");
 
-fn main() void {
+pub fn main() void {
     std.debug.print("Hello world!\n", .{});
 }

exercises/002_std.zig

@@ -11,7 +11,7 @@
 // Please complete the import below:
 //
 
-??? = @import("std");
+const std = @import("std");
 
 pub fn main() void {
     std.debug.print("Standard Library.\n", .{});

exercises/003_assignment.zig

@@ -34,12 +34,12 @@
 const std = @import("std");
 
 pub fn main() void {
-    const n: u8 = 50;
+    var n: u8 = 50;
     n = n + 5;
 
-    const pi: u8 = 314159;
+    const pi: u19 = 314159;
 
-    const negative_eleven: u8 = -11;
+    const negative_eleven: i8 = -11;
 
     // There are no errors in the next line, just explanation:
     // Perhaps you noticed before that the print function takes two

exercises/004_arrays.zig

@@ -27,7 +27,7 @@ pub fn main() void {
     // (Problem 1)
     // This "const" is going to cause a problem later - can you see what it is?
     // How do we fix it?
-    const some_primes = [_]u8{ 1, 3, 5, 7, 11, 13, 17, 19 };
+    var some_primes = [_]u8{ 1, 3, 5, 7, 11, 13, 17, 19 };
 
     // Individual values can be set with '[]' notation.
     // Example: This line changes the first prime to 2 (which is correct):
@@ -40,11 +40,11 @@ pub fn main() void {
     // (Problem 2)
     // Looks like we need to complete this expression. Use the example
     // above to set "fourth" to the fourth element of the some_primes array:
-    const fourth = some_primes[???];
+    const fourth = some_primes[3];
 
     // (Problem 3)
     // Use the len property to get the length of the array:
-    const length = some_primes.???;
+    const length = some_primes.len;
 
     std.debug.print("First: {}, Fourth: {}, Length: {}\n", .{
         first, fourth, length,

exercises/005_arrays2.zig

@@ -25,12 +25,12 @@ pub fn main() void {
     // (Problem 1)
     // Please set this array concatenating the two arrays above.
     // It should result in: 1 3 3 7
-    const leet = ???;
+    const leet = le ++ et;
 
     // (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 = [_]u8{ ??? } ** 3;
+    const bit_pattern = [_]u8{ 1, 0, 0, 1 } ** 3;
 
     // Okay, that's all of the problems. Let's see the results.
     //

exercises/006_strings.zig

@@ -24,18 +24,18 @@ pub fn main() void {
     // (Problem 1)
     // Use array square bracket syntax to get the letter 'd' from
     // the string "stardust" above.
-    const d: u8 = ziggy[???];
+    const d: u8 = ziggy[4];
 
     // (Problem 2)
     // Use the array repeat '**' operator to make "ha ha ha ".
-    const laugh = "ha " ???;
+    const laugh = "ha " ** 3;
 
     // (Problem 3)
     // Use the array concatenation '++' operator to make "Major Tom".
     // (You'll need to add a space as well!)
     const major = "Major";
     const tom = "Tom";
-    const major_tom = major ??? tom;
+    const major_tom = major ++ " " ++ tom;
 
     // That's all the problems. Let's see our results:
     std.debug.print("d={u} {s}{s}\n", .{ d, laugh, major_tom });

exercises/007_strings2.zig

@@ -15,9 +15,9 @@ const std = @import("std");
 
 pub fn main() void {
     const lyrics =
-        Ziggy played guitar
-        Jamming good with Andrew Kelley
-        And the Spiders from Mars
+        \\Ziggy played guitar
+        \\Jamming good with Andrew Kelley
+        \\And the Spiders from Mars
     ;
 
     std.debug.print("{s}\n", .{lyrics});

exercises/008_quiz.zig

@@ -19,7 +19,7 @@ pub fn main() void {
     // the idiomatic type to use for array indexing.
     //
     // There IS a problem on this line, but 'usize' isn't it.
-    const x: usize = 1;
+    var x: usize = 1;
 
     // Note: When you want to declare memory (an array in this
     // case) without putting anything in it, you can set it to
@@ -30,13 +30,14 @@ pub fn main() void {
     // 'lang' array we just created by indexing the array
     // 'letters' with the variable 'x'. As you can see above, x=1
     // to begin with.
+    //x = 1;
     lang[0] = letters[x];
 
     x = 3;
-    lang[???] = letters[x];
+    lang[1] = letters[x];
 
-    x = ???;
-    lang[2] = letters[???];
+    x = 5;
+    lang[2] = letters[x];
 
     // We want to "Program in Zig!" of course:
     std.debug.print("Program in {s}!\n", .{lang});

exercises/009_if.zig

@@ -21,7 +21,7 @@
 const std = @import("std");
 
 pub fn main() void {
-    const foo = 1;
+    const foo = true;
 
     // Please fix this condition:
     if (foo) {

exercises/010_if2.zig

@@ -10,7 +10,7 @@ pub fn main() void {
 
     // Please use an if...else expression to set "price".
     // If discount is true, the price should be $17, otherwise $20:
-    const price: u8 = if ???;
+    const price: u8 = if(discount) 17 else 20;
 
     std.debug.print("With the discount, the price is ${}.\n", .{price});
 }

exercises/011_while.zig

@@ -21,7 +21,7 @@ pub fn main() void {
     var n: u32 = 2;
 
     // Please use a condition that is true UNTIL "n" reaches 1024:
-    while (???) {
+    while (n < 1024 ) {
         // Print the current number
         std.debug.print("{} ", .{n});
 

exercises/012_while2.zig

@@ -25,7 +25,7 @@ pub fn main() void {
 
     // Please set the continue expression so that we get the desired
     // results in the print statement below.
-    while (n < 1000) : ??? {
+    while (n < 1000) : (n *= 2) {
         // Print the current number
         std.debug.print("{} ", .{n});
     }

exercises/013_while3.zig

@@ -24,8 +24,8 @@ pub fn main() void {
     while (n <= 20) : (n += 1) {
         // The '%' symbol is the "modulo" operator and it
         // returns the remainder after division.
-        if (n % 3 == 0) ???;
-        if (n % 5 == 0) ???;
+        if (n % 3 == 0) continue;
+        if (n % 5 == 0) continue;
         std.debug.print("{} ", .{n});
     }
 

exercises/014_while4.zig

@@ -18,7 +18,7 @@ pub fn main() void {
     // Oh dear! This while loop will go forever?!
     // Please fix this so the print statement below gives the desired output.
     while (true) : (n += 1) {
-        if (???) ???;
+        if (n == 4) break;
     }
 
     // Result: we want n=4

exercises/015_for.zig

@@ -15,7 +15,7 @@ pub fn main() void {
 
     std.debug.print("A Dramatic Story: ", .{});
 
-    for (???) |???| {
+    for (story) |scene| {
         if (scene == 'h') std.debug.print(":-)  ", .{});
         if (scene == 's') std.debug.print(":-(  ", .{});
         if (scene == 'n') std.debug.print(":-|  ", .{});

exercises/016_for2.zig

@@ -25,13 +25,14 @@ pub fn main() void {
     // the value of the place as a power of two for each bit.
     //
     // See if you can figure out the missing pieces:
-    for (bits, ???) |bit, ???| {
+    for (bits, 0..) |bit, i| {
         // Note that we convert the usize i to a u32 with
         // @intCast(), a builtin function just like @import().
         // We'll learn about these properly in a later exercise.
         const i_u32: u32 = @intCast(i);
         const place_value = std.math.pow(u32, 2, i_u32);
         value += place_value * bit;
+//        std.debug.print( "The current value is: {}.\n", .{place_value});
     }
 
     std.debug.print("The value of bits '1101': {}.\n", .{value});

exercises/017_quiz2.zig

@@ -9,18 +9,18 @@
 // Let's go from 1 to 16. This has been started for you, but there
 // are some problems. :-(
 //
-const std = import standard library;
+const std = @import ("std");
 
-function main() void {
+pub fn main() void {
     var i: u8 = 1;
     const stop_at: u8 = 16;
 
     // What kind of loop is this? A 'for' or a 'while'?
-    ??? (i <= stop_at) : (i += 1) {
+    while (i <= stop_at) : (i += 1) {
         if (i % 3 == 0) std.debug.print("Fizz", .{});
         if (i % 5 == 0) std.debug.print("Buzz", .{});
         if (!(i % 3 == 0) and !(i % 5 == 0)) {
-            std.debug.print("{}", .{???});
+            std.debug.print("{}", .{i});
         }
         std.debug.print(", ", .{});
     }

exercises/018_functions.zig

@@ -25,6 +25,6 @@ pub fn main() void {
 // We're just missing a couple things. One thing we're NOT missing is the
 // keyword "pub", which is not needed here. Can you guess why?
 //
-??? deepThought() ??? {
+fn deepThought() u8 {
     return 42; // Number courtesy Douglas Adams
 }

exercises/019_functions2.zig

@@ -22,7 +22,7 @@ pub fn main() void {
 // You'll need to figure out the parameter name and type that we're
 // expecting. The output type has already been specified for you.
 //
-fn twoToThe(???) u32 {
+fn twoToThe(my_number: u32) u32 {
     return std.math.pow(u32, 2, my_number);
     // std.math.pow(type, a, b) takes a numeric type and two
     // numbers of that type (or that can coerce to that type) and

exercises/020_quiz3.zig

@@ -21,8 +21,8 @@ pub fn main() void {
 //
 // This function prints, but does not return anything.
 //
-fn printPowersOfTwo(numbers: [4]u16) ??? {
-    loop (numbers) |n| {
+fn printPowersOfTwo(numbers: [4]u16) void {
+    for (numbers) |n| {
         std.debug.print("{} ", .{twoToThe(n)});
     }
 }
@@ -31,13 +31,13 @@ fn printPowersOfTwo(numbers: [4]u16) ??? {
 // exercise. But don't be fooled! This one does the math without the aid
 // of the standard library!
 //
-fn twoToThe(number: u16) ??? {
+fn twoToThe(number: u16) u16 {
     var n: u16 = 0;
     var total: u16 = 1;
 
-    loop (n < number) : (n += 1) {
+    while (n < number) : (n += 1) {
         total *= 2;
     }
 
-    return ???;
+    return total;
 }

exercises/021_errors.zig

@@ -9,7 +9,7 @@
 // "TooSmall". Please add it where needed!
 const MyNumberError = error{
     TooBig,
-    ???,
+    TooSmall,
     TooFour,
 };
 
@@ -26,7 +26,7 @@ pub fn main() void {
         if (number_error == MyNumberError.TooBig) {
             std.debug.print(">4. ", .{});
         }
-        if (???) {
+        if (number_error == MyNumberError.TooSmall) {
             std.debug.print("<4. ", .{});
         }
         if (number_error == MyNumberError.TooFour) {

exercises/022_errors2.zig

@@ -19,8 +19,7 @@ const std = @import("std");
 const MyNumberError = error{TooSmall};
 
 pub fn main() void {
-    var my_number: ??? = 5;
-
+    var my_number: MyNumberError!usize = 5;
     // Looks like my_number will need to either store a number OR
     // an error. Can you set the type correctly above?
     my_number = MyNumberError.TooSmall;

exercises/023_errors3.zig

@@ -12,14 +12,14 @@ const MyNumberError = error{TooSmall};
 
 pub fn main() void {
     const a: u32 = addTwenty(44) catch 22;
-    const b: u32 = addTwenty(4) ??? 22;
+    const b: u32 = addTwenty(4) catch 22;
 
     std.debug.print("a={}, b={}\n", .{ a, b });
 }
 
 // Please provide the return type from this function.
 // Hint: it'll be an error union.
-fn addTwenty(n: u32) ??? {
+fn addTwenty(n: u32) MyNumberError!u32 {
     if (n < 5) {
         return MyNumberError.TooSmall;
     } else {

exercises/024_errors4.zig

@@ -53,13 +53,19 @@ fn fixTooBig(n: u32) MyNumberError!u32 {
 }
 
 fn fixTooSmall(n: u32) MyNumberError!u32 {
+    return detectProblems(n) catch |err| {
+        if (err == MyNumberError.TooSmall) {
+            return 10;
+        }
+
+        return err;
+    };
     // Oh dear, this is missing a lot! But don't worry, it's nearly
     // identical to fixTooBig() above.
     //
     // If we get a TooSmall error, we should return 10.
     // If we get any other error, we should return that error.
     // Otherwise, we return the u32 number.
-    return detectProblems(n) ???;
 }
 
 fn detectProblems(n: u32) MyNumberError!u32 {

exercises/025_errors5.zig

@@ -25,9 +25,7 @@ pub fn main() void {
 fn addFive(n: u32) MyNumberError!u32 {
     // This function needs to return any error which might come back from detect().
     // Please use a "try" statement rather than a "catch".
-    //
-    const x = detect(n);
-
+    const x = try detect(n);
     return x + 5;
 }
 

exercises/026_hello2.zig

@@ -23,5 +23,5 @@ pub fn main() !void {
     // 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", .{});
 }

exercises/027_defer.zig

@@ -20,6 +20,6 @@ const std = @import("std");
 pub fn main() void {
     // Without changing anything else, please add a 'defer' statement
     // to this code so that our program prints "One Two\n":
-    std.debug.print("Two\n", .{});
+    defer std.debug.print("Two\n", .{});
     std.debug.print("One ", .{});
 }

exercises/028_defer2.zig

@@ -18,7 +18,7 @@ pub fn main() void {
 fn printAnimal(animal: u8) void {
     std.debug.print("(", .{});
 
-    std.debug.print(") ", .{}); // <---- how?!
+    defer std.debug.print(") ", .{}); // <---- how?!
 
     if (animal == 'g') {
         std.debug.print("Goat", .{});

exercises/029_errdefer.zig

@@ -32,7 +32,7 @@ fn makeNumber() MyErr!u32 {
 
     // Please make the "failed" message print ONLY if the makeNumber()
     // function exits with an error:
-    std.debug.print("failed!\n", .{});
+    errdefer std.debug.print("failed!\n", .{});
 
     var num = try getNumber(); // <-- This could fail!
 

exercises/030_switch.zig

@@ -46,6 +46,9 @@ pub fn main() void {
             // match for every possible value).  Please add an "else"
             // to this switch to print a question mark "?" when c is
             // not one of the existing matches.
+            else => {
+                std.debug.print("?", .{});
+            },
         }
     }
 

exercises/031_switch2.zig

@@ -31,6 +31,9 @@ pub fn main() void {
             26 => 'Z',
             // As in the last exercise, please add the 'else' clause
             // and this time, have it return an exclamation mark '!'.
+            else => {
+                return std.debug.print("!", .{});
+            },
         };
 
         std.debug.print("{c}", .{real_char});

exercises/032_unreachable.zig

@@ -35,6 +35,9 @@ pub fn main() void {
             3 => {
                 current_value *= current_value;
             },
+            else => {
+                unreachable;
+            },
         }
 
         std.debug.print("{} ", .{current_value});

exercises/033_iferror.zig

@@ -39,6 +39,7 @@ pub fn main() void {
             std.debug.print("={}. ", .{value});
         } else |err| switch (err) {
             MyNumberError.TooBig => std.debug.print(">4. ", .{}),
+            MyNumberError.TooSmall => std.debug.print("<4. ", .{}),
             // Please add a match for TooSmall here and have it print: "<4. "
         }
     }

exercises/034_quiz4.zig

@@ -9,10 +9,16 @@ const std = @import("std");
 
 const NumError = error{IllegalNumber};
 
-pub fn main() void {
+pub fn main() !void {
     const stdout = std.io.getStdOut().writer();
 
-    const my_num: u32 = getNumber();
+    const my_num: u32 = try getNumber();
+
+    // if (my_num) |value| {
+    // stdout("ZIG! {!}", .{value});
+    // } else |err| switch (err) {
+    // NumError.IllegalNumber => 42,
+    // }
 
     try stdout.print("my_num={}\n", .{my_num});
 }

exercises/100_for4.zig

@@ -41,12 +41,12 @@ pub fn main() void {
 
     for (hex_nums, ???) |hn, ???| {
         if (hn != dn) {
-            std.debug.print("Uh oh! Found a mismatch: {d} vs {d}\n", .{ hn, dn });
+            print("Uh oh! Found a mismatch: {d} vs {d}\n", .{ hn, dn });
             return;
         }
     }
 
-    std.debug.print("Arrays match!\n", .{});
+    print("Arrays match!\n", .{});
 }
 //
 // You are perhaps wondering what happens if one of the two lists

exercises/107_files2.zig

@@ -40,7 +40,7 @@ pub fn main() !void {
     // okay, seems like a threat of violence is not the answer in this case
     // can you go here to find a way to read the content?
     // https://ziglang.org/documentation/master/std/#std.fs.File
-    // hint: you might find two answers that are both vaild in this case
+    // hint: you might find two answers that are both valid in this case
     const bytes_read = zig_read_the_file_or_i_will_fight_you(&content);
 
     // Woah, too screamy. I know you're excited for zigling time but tone it down a bit.

exercises/108_labeled_switch.zig

@@ -15,11 +15,11 @@
 //                  1 => { op = 2; continue; },
 //                  2 => { op = 3; continue; },
 //                  3 => return,
-//                  4 => {},
+//                  else => {},
 //              }
 //              break;
 //          }
-//      std.debug.print("This statement cannot be reached");
+//      std.debug.print("This statement cannot be reached\n", .{});
 //      }
 //
 // By combining all we've learned so far, we can now proceed with a labeled switch
@@ -36,7 +36,7 @@
 //              3 => return,
 //              else => {},
 //          }
-//          std.debug.print("This statement cannot be reached");
+//          std.debug.print("This statement cannot be reached\n", .{});
 //      }
 //
 // The flow of execution on this second case is:
@@ -45,13 +45,12 @@
 //     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.
-//  5. In this example as the input has no clear exhaustive patterns but a essentially
-//      any u8 integer, we need do need to handle any case that is not explicitly handled
-//      by using the `else => {}` branch as a default case.
+//  4. Finally we get to case '3', where we return from the function as a whole,
+//     so the debug statement is never executed.
+//  5. In this example, since the input does not have clear, exhaustive patterns and
+//     can essentially be any 'u8' integer, we need to handle all cases not explicitly
+//     covered by using the 'else => {}' branch as the default case.
 //
-// Since step 4 or a break stament do not exist in this switch, the debug statement is
-// never executed
 //
 const std = @import("std");
 

patches/patches/100_for4.patch

@@ -7,5 +7,5 @@
 -    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 });
+             print("Uh oh! Found a mismatch: {d} vs {d}\n", .{ hn, dn });
              return;

patches/patches/107_files2.patch

@@ -42,7 +42,7 @@
 -    // can you go here to find a way to read the content?
 +    // can you go here to find a way to read the content ?
      // https://ziglang.org/documentation/master/std/#std.fs.File
-     // hint: you might find two answers that are both vaild in this case
+     // hint: you might find two answers that are both valid in this case
 -    const bytes_read = zig_read_the_file_or_i_will_fight_you(&content);
 +    const bytes_read = try file.read(&content);