Comments

comments.zig

  1. const expect = @import("std").testing.expect;
  3. test "comments" {
  4.     // Comments in Zig start with "//" and end at the next LF byte (end of line).
  5.     // The below line is a comment, and won't be executed.
  7.     //expect(false);
  9.     const x = true;  // another comment
  10.     expect(x);
  11. }
  1. $ zig test comments.zig
  2. 1/1 test "comments"... OK
  3. 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.

  1. /// A structure for storing a timestamp, with nanosecond precision (this is a
  2. /// multiline doc comment).
  3. const Timestamp = struct {
  4.     /// The number of seconds since the epoch (this is also a doc comment).
  5.     seconds: i64,  // signed so we can represent pre-1970 (not a doc comment)
  6.     /// The number of nanoseconds past the second (doc comment again).
  7.     nanos: u32,
  9.     /// Returns a `Timestamp` struct representing the Unix epoch; that is, the
  10.     /// moment of 1970 Jan 1 00:00:00 UTC (this is a doc comment too).
  11.     pub fn unixEpoch() Timestamp {
  12.         return Timestamp{
  13.             .seconds = 0,
  14.             .nanos = 0,
  15.         };
  16.     }
  17. };

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.

Top-Level Doc Comments

User documentation that doesn’t belong to whatever immediately follows it, like package-level documentation, goes in top-level doc comments. A top-level doc comment is one that begins with two slashes and an exclamation point: //!.

  1. //! This module provides functions for retrieving the current date and
  2. //! time with varying degrees of precision and accuracy. It does not
  3. //! depend on libc, but will use functions from it if available.