diff options
| -rw-r--r-- | build.zig | 6 | ||||
| -rw-r--r-- | exercises/44_quiz5.zig | 2 | ||||
| -rw-r--r-- | exercises/46_optionals2.zig | 46 | ||||
| -rw-r--r-- | patches/patches/46_optionals2.patch | 11 |
4 files changed, 64 insertions, 1 deletions
@@ -240,7 +240,11 @@ const exercises = [_]Exercise{ .main_file = "45_optionals.zig", .output = "The Ultimate Answer: 42.", }, - // optional fields (elephant tail - no longer need circular) + .{ + .main_file = "46_optionals2.zig", + .output = "Elephant A. Elephant B. Elephant C.", + .hint = "Elephants!", + }, // super-simple struct method // use struct method for elephant tails // quiz: add elephant trunk (like tail)! diff --git a/exercises/44_quiz5.zig b/exercises/44_quiz5.zig index 88e0ff7..a3289e9 100644 --- a/exercises/44_quiz5.zig +++ b/exercises/44_quiz5.zig @@ -28,6 +28,8 @@ pub fn main() void { elephantC.tail = &elephantA; visitElephants(&elephantA); + + std.debug.print("\n", .{}); } // This function visits all elephants once, starting with the diff --git a/exercises/46_optionals2.zig b/exercises/46_optionals2.zig new file mode 100644 index 0000000..11f37aa --- /dev/null +++ b/exercises/46_optionals2.zig @@ -0,0 +1,46 @@ +// +// Now that we have optional types, we can apply them to structs. +// The last time we checked in with our elephants, we had to link +// all three of them together in a "circle" so that the last tail +// linked to the first elephant. This is because we had NO CONCEPT +// of a tail that didn't point to another elephant! +// +const std = @import("std"); // single quotes + +const Elephant = struct { + letter: u8, + tail: *Elephant = undefined, // <---- make this optional! + visited: bool = false, +}; + +pub fn main() void { + var elephantA = Elephant{ .letter = 'A' }; + var elephantB = Elephant{ .letter = 'B' }; + var elephantC = Elephant{ .letter = 'C' }; + + // Link the elephants so that each tail "points" to the next. + elephantA.tail = &elephantB; + elephantB.tail = &elephantC; + + visitElephants(&elephantA); + + std.debug.print("\n", .{}); +} + +// This function visits all elephants once, starting with the +// first elephant and following the tails to the next elephant. +fn visitElephants(first_elephant: *Elephant) void { + var e = first_elephant; + + while (!e.visited) { + std.debug.print("Elephant {u}. ", .{e.letter}); + e.visited = true; + + // We should stop once we encounter a tail that + // does NOT point to another element. What can + // we put here to make that happen? + if (e.tail == null) ???; + + e = e.tail.?; + } +} diff --git a/patches/patches/46_optionals2.patch b/patches/patches/46_optionals2.patch new file mode 100644 index 0000000..18284da --- /dev/null +++ b/patches/patches/46_optionals2.patch @@ -0,0 +1,11 @@ +12c12 +< tail: *Elephant = undefined, // <---- make this optional! +--- +> tail: ?*Elephant = undefined, +39,42c39 +< // We should stop once we encounter a tail that +< // does NOT point to another element. What can +< // we put here to make that happen? +< if (e.tail == null) ???; +--- +> if (e.tail == null) break; |