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113 lines
2.5 KiB
Markdown
113 lines
2.5 KiB
Markdown
---
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id: f4c04f44-c7c3-4fa0-a4d6-e78995257b9c
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title: Rust Comments
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---
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# Basics
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In Rust, the idiomatic comment style starts a comment with two slashes,
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and the comment continues until the end of the line. For comments that
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extend beyond a single line, you’ll need to include // on each line,
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like this:
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``` rust
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// So we’re doing something complicated here, long enough that we need
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// multiple lines of comments to do it! Whew! Hopefully, this comment will
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// explain what’s going on.
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```
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Comments can also be placed at the end of lines containing code:
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``` rust
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fn main() {
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println!("tralala") // This prints something
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}
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```
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But if you're a sane person you'll comment above the code you're
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annotating
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``` rust
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// This prints something
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fn main() {
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println!("tralala")
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}
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```
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# Documentation comments
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## */*
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This is like phpdoc, but for Rust. Documentation comments use three
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slashes `///` and support Markdown notation:
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``` rust
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/// Adds one to the number given.
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///
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/// # Examples
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///
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/// ```
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/// let arg = 5;
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/// let answer = my_crate::add_one(arg);
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///
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/// assert_eq!(6, answer);
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/// ```
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pub fn add_one(x: i32) -> i32 {
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x + 1
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}
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```
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Run `cargo doc` to generate HTML documentation from the comments.
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`cargo doc --open` will open documentation in the browser.
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### Commonly used sections
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1. Panics
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The scenarios in which the function being documented could panic.
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Callers of the function who don’t want their programs to panic
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should make sure they don’t call the function in these situations.
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2. Errors
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If the function returns a `Result`, describing the kinds of errors
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that might occur and what conditions might cause those errors to be
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returned can be helpful to callers so they can write code to handle
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the different kinds of errors in different ways.
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3. Safety
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If the function is `unsafe` to call, there should be a section
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explaining why the function is unsafe and covering the invariants
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that the function expects callers to uphold.
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## //!
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This is used for general comments:
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``` rust
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//! # My Crate
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//!
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//! `my_crate` is a collection of utilities to make performing certain
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//! calculations more convenient.
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/// Adds one to the number given.
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// --snip--
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///
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/// # Examples
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///
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/// ```
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/// let arg = 5;
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/// let answer = my_crate::add_one(arg);
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///
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/// assert_eq!(6, answer);
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/// ```
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pub fn add_one(x: i32) -> i32 {
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x + 1
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}
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```
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# Changes
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- [Linking To Items By Name](20201119170237-linking_to_items_by_name)
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- [Search Aliases](20201119170710-search_aliases)
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