Comments

Comments

comments.zig

const assert = @import("std").debug.assert;

test "comments" {
    // Comments in Zig start with "//" and end at the next LF byte (end of line).
    // The below line is a comment, and won't be executed.

    //assert(false);

    const x = true;  // another comment
    assert(x);
}
``` ```
$ zig test comments.zig
1/1 test "comments"...OK
All 1 tests passed.

There are no multiline comments in Zig (e.g. like /* */ comments in C). This helps allow Zig to have the property that each line of code can be tokenized out of context.

Doc comments

A doc comment is one that begins with exactly three slashes (i.e. /// but not ////); multiple doc comments in a row are merged together to form a multiline doc comment. The doc comment documents whatever immediately follows it.

/// A structure for storing a timestamp, with nanosecond precision (this is a
/// multiline doc comment).
const Timestamp = struct {
    /// The number of seconds since the epoch (this is also a doc comment).
    seconds: i64,  // signed so we can represent pre-1970 (not a doc comment)
    /// The number of nanoseconds past the second (doc comment again).
    nanos: u32,

    /// Returns a `Timestamp` struct representing the Unix epoch; that is, the
    /// moment of 1970 Jan 1 00:00:00 UTC (this is a doc comment too).
    pub fn unixEpoch() Timestamp {
        return Timestamp{
            .seconds = 0,
            .nanos = 0,
        };
    }
};

Doc comments are only allowed in certain places; eventually, it will become a compile error to have a doc comment in an unexpected place, such as in the middle of an expression, or just before a non-doc comment.