mirror of
https://codeberg.org/andyscott/ziglings.git
synced 2024-11-13 21:40:46 -05:00
51 lines
1.5 KiB
Zig
51 lines
1.5 KiB
Zig
//
|
|
// 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:
|
|
const 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;
|
|
//
|