52 lines
1.5 KiB
Zig
52 lines
1.5 KiB
Zig
//
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// Sometimes you know that a variable might hold a value or
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// it might not. Zig has a neat way of expressing this idea
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// called Optionals. An optional type just has a '?' like this:
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//
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// var foo: ?u32 = 10;
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//
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// Now foo can store a u32 integer OR null (a value storing
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// the cosmic horror of a value NOT EXISTING!)
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//
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// foo = null;
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//
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// if (foo == null) beginScreaming();
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//
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// Before we can use the optional value as the non-null type
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// (a u32 integer in this case), we need to guarantee that it
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// isn't null. One way to do this is to THREATEN IT with the
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// "orelse" statement.
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//
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// var bar = foo orelse 2;
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//
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// Here, bar will either equal the u32 integer value stored in
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// foo, or it will equal 2 if foo was null.
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//
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const std = @import("std");
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pub fn main() void {
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const result = deepThought();
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// Please threaten the result so that answer is either the
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// integer value from deepThought() OR the number 42:
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var answer: u8 = result orelse 42;
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std.debug.print("The Ultimate Answer: {}.\n", .{answer});
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}
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fn deepThought() ?u8 {
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// It seems Deep Thought's output has declined in quality.
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// But we'll leave this as-is. Sorry Deep Thought.
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return null;
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}
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// Blast from the past:
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//
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// Optionals are a lot like error union types which can either
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// hold a value or an error. Likewise, the orelse statement is
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// like the catch statement used to "unwrap" a value or supply
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// a default value:
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//
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// var maybe_bad: Error!u32 = Error.Evil;
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// var number: u32 = maybe_bad catch 0;
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//
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