defer in Zig

Cleanup declared next to the thing it cleans: defer runs at scope exit, in reverse.

const std = @import("std");

fn brew() void {
    // defer runs at scope exit, last-declared first.
    std.debug.print("kettle on\n", .{});
    defer std.debug.print("kettle off\n", .{});
    defer std.debug.print("pour the cup\n", .{});
    std.debug.print("three minutes steeping\n", .{});
}

pub fn main() void {
    brew();
    std.debug.print("milk first, obviously\n", .{});
}

How it works

1. Each defer is registered when the line is reached, not when it runs.
2. At scope exit they fire last-declared first: pour the cup, then kettle off.
3. The pattern keeps acquisition and release adjacent in the source.

Keywords and builtins used here

• const
• defer
• fn
• pub
• void

The run, in numbers

Lines

14

Characters to type

355

Tokens

112

Three-star pace

75 tpm

At the three-star pace of 75 tokens a minute, this run takes about 90 seconds.

Type this snippet

Step 3 of 3 in Errors, step 9 of 27 in Language basics.

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defer in other languages

• Odin
• Swift