From 545573fc84c2b8e3f281de7eb9bc52281536d5b3 Mon Sep 17 00:00:00 2001 From: Dave Gauer Date: Sun, 14 Feb 2021 10:49:09 -0500 Subject: Added ex 45 optionals (And secretly added the patches/ dir. Don't tell anybody!) --- exercises/45_optionals.zig | 52 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+) create mode 100644 exercises/45_optionals.zig (limited to 'exercises/45_optionals.zig') diff --git a/exercises/45_optionals.zig b/exercises/45_optionals.zig new file mode 100644 index 0000000..815ba75 --- /dev/null +++ b/exercises/45_optionals.zig @@ -0,0 +1,52 @@ +// +// Sometimes you know that a variable might hold a value or +// it might not. Zig has a neat way of expressing this idea +// called Optionals. An optional type just has a '?' like this: +// +// var foo: ?u32 = 10; +// +// Now foo can store a u32 integer OR null (a value storing +// the cosmic horror of a value NOT EXISTING!) +// +// foo = null; +// +// if (foo == null) beginScreaming(); +// +// Before we can use the optional value as the non-null type +// (a u32 integer in this case), we need to guarantee that it +// isn't null. One way to do this is to THREATEN IT with the +// "orelse" statement. +// +// var bar = foo orelse 2; +// +// Here, bar will either equal the u32 integer value stored in +// foo, or it will equal 2 if foo was null. +// +const std = @import("std"); + +pub fn main() void { + const result = deepThought(); + + // Please threaten the result so that answer is either the + // integer value from deepThought() OR the number 42: + var answer: u8 = result; + + std.debug.print("The Ultimate Answer: {}.\n",.{answer}); +} + +fn deepThought() ?u8 { + // It seems Deep Thought's output has declined in quality. + // But we'll leave this as-is. Sorry Deep Thought. + return null; +} +// +// Blast from the past: +// +// Optionals are a lot like error union types which can either +// hold a value or an error. Likewise, the orelse statement is +// like the catch statement used to "unwrap" a value or supply +// a default value: +// +// var maybe_bad: Error!u32 = Error.Evil; +// var number: u32 = maybe_bad catch 0; +// -- cgit v1.2.3-70-g09d2