Inserted ex. 32 unreachable, added quiz4.

32_unreachable.zig

@@ -0,0 +1,38 @@
+//
+// Zig has an "unreachable" statement. Use it when you want to tell the
+// compiler that a branch of code should never be executed and that the
+// mere act of reaching it is an error.
+//
+//     if (true) {
+//         ...
+//     } else {
+//         unreachable;
+//     }
+//
+// Here we've made a little virtual machine that performs mathematical
+// operations on a single numeric value. It looks great but there's one
+// little problem: the switch statement doesn't cover every possible
+// value of a u8 number!
+//
+// WE know there are only three operations but Zig doesn't. Use the
+// unreachable statement to make the switch complete. Or ELSE. :-)
+// 
+const std = @import("std");
+
+pub fn main() void {
+    const operations = [_]u8{ 1, 1, 1, 3, 2, 2 };
+
+    var current_value: u32 = 0;
+
+    for (operations) |op| {
+        switch (op) {
+            1  => { current_value += 1; },
+            2  => { current_value -= 1; },
+            3  => { current_value *= current_value; },
+        }
+
+        std.debug.print("{} ", .{current_value});
+    }
+
+    std.debug.print("\n", .{});
+}

34_quiz4.zig

@@ -0,0 +1,24 @@
+//
+// Quiz time. See if you can make this program work!
+//
+// Solve this any way you like, just be sure the output is:
+//
+//     my_num=42
+//
+const std = @import("std");
+
+const NumError = error{ IllegalNumber };
+
+pub fn main() void {
+    const stdout = std.io.getStdOut().writer();
+
+    const my_num: u32 = getNumber();
+
+    try stdout.print("my_num={}\n", .{my_num});
+}
+
+// Just don't modify this function. It's "perfect" the way it is. :-)
+fn getNumber() NumError!u32 {
+    if( false ) return NumError.IllegalNumber;
+    return 42;
+}

README.md

@@ -66,10 +66,10 @@ Planned exercises:
 * [x] While
 * [x] For
 * [x] Functions
-* [x] Errors
-* [x] Defer
+* [x] Errors (error/try/catch/if-else-err)
+* [x] Defer (and errdefer)
 * [x] Switch
-* [ ] Unreachable
+* [x] Unreachable
 * [ ] Pointers
 * [ ] Pointer sized integers
 * [ ] Multi pointers

ziglings

@@ -99,8 +99,9 @@ check_it 28_defer2.zig "(Goat) (Cat) (Dog) (Dog) (Goat) (Unknown) done."
 check_it 29_errdefer.zig "Getting number...got 5. Getting number...failed!"
 check_it 30_switch.zig "ZIG?"
 check_it 31_switch2.zig "ZIG!"
-check_it 32_iferror.zig "2<4. 3<4. 4=4. 5>4. 6>4." "Seriously, what's the deal with fours?"
-#check_it 33_quiz4.zig "foo" "Can you make this work?"
+check_it 32_unreachable.zig "1 2 3 9 8 7"
+check_it 33_iferror.zig "2<4. 3<4. 4=4. 5>4. 6>4." "Seriously, what's the deal with fours?"
+check_it 34_quiz4.zig "my_num=42" "Can you make this work?"
 
 echo
 echo "    __   __          _ "