rust-cookbook/book/print.html
2017-02-25 21:56:57 -06:00

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<ul class="chapter"><li class="affix"><a href="pages/table_of_contents.html">Table of Contents</a></li><li class="affix"><a href="pages/error_handling_note.html">A Note About Error Handling</a></li><li><a href="pages/math.html"><strong>1.</strong> Math</a></li><li><ul class="section"><li><a href="pages/rand.html"><strong>1.1.</strong> rand</a></li></ul></li><li><a href="pages/IO.html"><strong>2.</strong> IO</a></li><li><ul class="section"><li><a href="pages/byteorder.html"><strong>2.1.</strong> Byteorder</a></li><li><a href="pages/file_io.html"><strong>2.2.</strong> File IO</a></li><li><a href="pages/cli_parsing.html"><strong>2.3.</strong> Command Line Parsing</a></li></ul></li><li><a href="pages/serialization.html"><strong>3.</strong> Serialization</a></li><li><ul class="section"><li><a href="pages/json.html"><strong>3.1.</strong> JSON</a></li><li><a href="pages/toml.html"><strong>3.2.</strong> TOML</a></li></ul></li><li><a href="pages/contributing.html">Contributing</a></li></ul>
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<a class="header" href="#cookin-with-rust" name="cookin-with-rust"><h1>Cookin' with Rust</h1></a>
<p>A practical guide to the Rust crate ecosystem.</p>
<a class="header" href="#recipes" name="recipes"><h2>Recipes</h2></a>
<ul>
<li><a href="pages/byteorder.html">Byteorder</a> <a href="https://docs.rs/byteorder"><img src="https://img.shields.io/crates/v/rustc-serialize.svg?label=byteorder" alt="byteorder-badge" /></a></li>
<li><a href="pages/fileio.html">File IO</a> <a href="https://doc.rust-lang.org/std/fs/struct.File.html"><img src="https://img.shields.io/crates/v/rustc-serialize.svg?label=file" alt="file-badge" /></a></li>
<li><a href="pages/cliparsing.html">Command Line Parsing</a> <a href="https://kbknapp.github.io/clap-rs/clap/struct.Arg.html"><img src="https://img.shields.io/crates/v/rustc-serialize.svg?label=clap" alt="clap-badge" /></a></li>
<li><a href="pages/json.html">JSON</a> <a href="http://json.rs/doc/json"><img src="https://img.shields.io/crates/v/rustc-serialize.svg?label=json" alt="json-badge" /></a></li>
<li><a href="pages/toml.html">TOML</a> <a href="http://alexcrichton.com/toml-rs/toml/"><img src="https://img.shields.io/crates/v/rustc-serialize.svg?label=toml" alt="toml-badge" /></a></li>
<li><a href="pages/rand.html">rand</a> <a href="https://doc.rust-lang.org/rand/rand/index.html"><img src="https://img.shields.io/crates/v/rand.svg?label=rand" alt="rand-badge" /></a></li>
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<a class="header" href="#contributing" name="contributing"><h2>Contributing</h2></a>
<p>If you'd like to make changes to the project, please see <a href="CONTRIBUTING.html">this guide</a>.</p>
<a class="header" href="#license" name="license"><h2>License</h2></a>
<p>MIT/Apache-2.0</p>
<!-- Links -->
<a class="header" href="#a-note-about-error-handling" name="a-note-about-error-handling"><h1>A note about error handling</h1></a>
<p>Error handling in Rust is robust when done correctly, but in today's
Rust it requires a fair bit of boilerplate. Because of this one often
sees Rust examples filled with <code>unwrap</code> calls instead of proper error
handling.</p>
<p>Since these recipes are intended to be reused as-is and encourage best
practices, they set up error handling correctly, and when necessary to
reduce boilerplate, they use the [error-chain] crate.</p>
<p>The code for this setup generally looks like:</p>
<pre><code class="language-rust">#[macro_use]
extern crate error_chain;
mod errors {
error_chain! {
foreign_links {
Io(::std::io::Error);
}
}
}
use errors::*;
fn main() { run().unwrap() }
fn run() -&gt; Result&lt;()&gt; {
use std::io::Write;
let ref mut stdout = ::std::io::stdout();
writeln!(stdout, &quot;hello, world&quot;)?;
Ok(())
}
</code></pre>
<p>This is using the <code>error_chain!</code> macro to define a custom <code>Error</code>
and <code>Result</code> type, along with an automatic conversion from
the common <code>::std::io::Error</code> type. The automatic conversion
makes the <code>?</code> operator work</p>
<p>For more background on error handling in Rust, read [this page of the Rust book][error-docs] and [this blog post][error-blog].</p>
<a class="header" href="#math" name="math"><h1>Math</h1></a>
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<a class="header" href="#rand" name="rand"><h1>rand</h1></a>
<a class="header" href="#random-number-generators-and-other-randomness-functionality" name="random-number-generators-and-other-randomness-functionality"><h2>Random number generators and other randomness functionality</h2></a>
<p><a href="https://doc.rust-lang.org/rand/rand/index.html"><img src="https://img.shields.io/crates/v/rand.svg?label=rand" alt="rand-badge" /></a></p>
<a class="header" href="#example-monte-carlo-integration" name="example-monte-carlo-integration"><h3>Example: Monte carlo integration</h3></a>
<p>Use the <code>rand</code> crate to generate random samples and approximate
$\int_{0}^{\pi} sin(x) dx$ using monte carlo.</p>
<p><em>Key concepts:</em></p>
<ul>
<li>Creating thread-specific RNG</li>
<li>Generating real numbers over an interval</li>
</ul>
<pre><code class="language-rust">extern crate rand;
use rand::Rng;
use std::f32;
/// f(x) = sin(x)
fn f(x: f32) -&gt; f32 {
x.sin()
}
/// Compute integral of f(x) dx from a to b using n samples
fn monte_carlo(a: f32, b: f32, n: u32) -&gt; f32 {
// Generate numbers specific to this thread
let mut rng = rand::thread_rng();
let mut samples: Vec&lt;f32&gt; = Vec::new();
// Generate n samples between [a, b)
for _ in 0..n {
samples.push(rng.gen_range(a, b));
}
// Find function values
let mut sum = 0.;
for x in samples {
sum += f(x);
}
// Returns average of samples over interval
(b - a) / n as f32 * sum
}
fn main() {
println!(&quot;{}&quot;, monte_carlo(0., f32::consts::PI, 200_000));
}
</code></pre>
<a class="header" href="#example-generating-random-rgb-colors" name="example-generating-random-rgb-colors"><h3>Example: Generating random RGB colors</h3></a>
<p>A <em>trait</em> is a language feature that tells the Rust compiler about functionality a type must provide.</p>
<p>Rust has the powerful ability to create traits for your own types.
One example is <code>rand::Rand</code>. Any type that implements Rand can use the
polymorphic function <code>Rng::gen()</code> to generate random types.</p>
<p><em>Key concepts:</em></p>
<ul>
<li>Generating a random structure</li>
</ul>
<pre><code class="language-rust">extern crate rand;
use rand::Rng;
use rand::Rand;
#[derive(Debug)] // Allows us to print using {:?} format specifier
struct Color { // RGB Color struct
r: f64,
g: f64,
b: f64,
}
// Implementing Rand for type Color
impl Rand for Color {
fn rand&lt;R: Rng&gt;(rng: &amp;mut R) -&gt; Self {
Color {r: rng.next_f64(), b: rng.next_f64(), g: rng.next_f64()}
}
}
fn main() {
// Generate a random Color and print to stdout
let mut rng = rand::thread_rng();
let c: Color = rng.gen();
println!(&quot;{:?}&quot;, c);
}
</code></pre>
<!-- Links -->
<a class="header" href="#byteorder" name="byteorder"><h1>Byteorder</h1></a>
<p><a href="https://docs.rs/byteorder"><img src="https://img.shields.io/crates/v/rustc-serialize.svg?label=byteorder" alt="byteorder-badge" /></a></p>
<a class="header" href="#read-and-write-integers-in-little-endian-byte-order" name="read-and-write-integers-in-little-endian-byte-order"><h2>Read and write integers in little-endian byte order</h2></a>
<pre><code class="language-rust">extern crate byteorder;
use std::io::Cursor;
use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
#[derive(Default, Eq, PartialEq, Debug)]
struct Payload {
kind: u8,
value: u16,
}
fn run() -&gt; Result&lt;()&gt; {
let original_payload = Payload::default();
let encoded_buf = encode(&amp;original_payload)?;
let decoded_payload = decode(&amp;encoded_buf)?;
assert_eq!(original_payload, decoded_payload);
Ok(())
}
fn encode(payload: &amp;Payload) -&gt; Result&lt;Vec&lt;u8&gt;&gt; {
let mut wtr = vec![];
wtr.write_u8(payload.kind)?;
wtr.write_u16::&lt;LittleEndian&gt;(payload.value)?;
Ok(wtr)
}
fn decode(buf: &amp;[u8]) -&gt; Result&lt;Payload&gt; {
let mut rdr = Cursor::new(buf);
Ok(Payload {
kind: rdr.read_u8()?,
value: rdr.read_u16::&lt;LittleEndian&gt;()?,
})
}
#[macro_use]
extern crate error_chain;
mod errors {
error_chain! {
foreign_links {
Io(::std::io::Error);
}
}
}
use errors::*;
fn main() { run().unwrap() }
</code></pre>
<!-- Links -->
<a class="header" href="#json" name="json"><h1>JSON</h1></a>
<p><a href="http://json.rs/doc/json"><img src="https://img.shields.io/crates/v/rustc-serialize.svg?label=json" alt="json-badge" /></a></p>
<a class="header" href="#json-implementation-in-rust" name="json-implementation-in-rust"><h2>JSON implementation in Rust:</h2></a>
<p>The example below shows two simple ways to embed JSON in Rust.
The first method parses block JSON as a block using the parse method from the json crate. It then unwraps the parsed JSON.
The second method instantiates an object as JSON using the object macro. Key value relationships are easily set using <code>=&gt;</code>.</p>
<p>After demonstrating two simple ways to write JSON, the <code>assert_eq!</code> macro ensures equivalence.</p>
<pre><code class="language-rust">#[macro_use]
extern crate json;
fn main(){
let parsed_data = json::parse(r#&quot;
{
&quot;userid&quot;: 103609,
&quot;verified&quot;: true,
&quot;access_privelages&quot;: [
&quot;user&quot;,
&quot;admin&quot;
]
}
&quot;#).unwrap();
let instantiated_data = object!{
&quot;userid&quot; =&gt; 103609,
&quot;verified&quot; =&gt; true,
&quot;access_privelages&quot; =&gt; array![
&quot;user&quot;,
&quot;admin&quot;
]
};
assert_eq!(parsed_data, instantiated_data);
}
</code></pre>
<a class="header" href="#license" name="license"><h1>License</h1></a>
<p>MIT/Apache-2.0</p>
<!-- Links -->
<a class="header" href="#toml" name="toml"><h1>TOML</h1></a>
<p><a href="http://alexcrichton.com/toml-rs/toml/"><img src="https://img.shields.io/crates/v/rustc-serialize.svg?label=toml" alt="toml-badge" /></a></p>
<p>Parse TOML into a <code>toml::Value</code> and then operate on it:</p>
<pre><code class="language-rust">extern crate toml;
fn main() {
let toml_source = &quot;
[package]
name = \&quot;your package!\&quot;
version = \&quot;0.1.0\&quot;
authors = [\&quot;You! &lt;you@example.org&gt;\&quot;]
[dependencies]
cool = \&quot;0.2.1\&quot;&quot;;
let package_info = toml_source.parse::&lt;toml::Value&gt;().unwrap();
assert_eq!(package_info[&quot;dependencies&quot;][&quot;cool&quot;].as_str(), Some(&quot;0.2.1&quot;));
assert_eq!(package_info[&quot;package&quot;][&quot;name&quot;].as_str(), Some(&quot;your package!&quot;));
}
</code></pre>
<p>Parse TOML into your own structs using the <code>serde</code> crate:</p>
<pre><code class="language-rust">
extern crate toml;
#[macro_use]
extern crate serde_derive;
extern crate serde;
#[derive(Deserialize)]
struct Config {
package: Package,
dependencies: std::collections::HashMap&lt;String, String&gt;,
}
#[derive(Deserialize)]
struct Package {
name: String,
version: String,
authors: Vec&lt;String&gt;,
}
fn main() {
let toml_source = &quot;
[package]
name = \&quot;your package!\&quot;
version = \&quot;0.1.0\&quot;
authors = [\&quot;You! &lt;you@example.org&gt;\&quot;]
[dependencies]
cool = \&quot;0.2.1\&quot;&quot;;
let package_info : Config = toml::from_str(toml_source).unwrap();
assert_eq!(package_info.package.name, &quot;your package!&quot;);
assert_eq!(package_info.package.version, &quot;0.1.0&quot;);
assert_eq!(package_info.package.authors, vec![&quot;You! &lt;you@example.org&gt;&quot;]);
assert_eq!(package_info.dependencies[&quot;cool&quot;], &quot;0.2.1&quot;);
}
</code></pre>
<a class="header" href="#license" name="license"><h1>License</h1></a>
<p>MIT/Apache-2.0</p>
<!-- Links -->
<a class="header" href="#contributing-to-the-rust-cookbook" name="contributing-to-the-rust-cookbook"><h1>Contributing to the Rust Cookbook</h1></a>
<p>Have something useful to add to the Rust Cookbook? We'd love to have it!</p>
<p>This document contains information and guidelines that you should read before
contributing to the project. If you think something in this document should change,
feel free propose a change in a pull request.</p>
<a class="header" href="#table-of-contents" name="table-of-contents"><h2>Table of Contents</h2></a>
<ul>
<li><a href="#getting-started">Getting Started</a></li>
<li><a href="#how-to-contribute">How to Contribute</a></li>
<li><a href="#crates">Crates</a></li>
<li><a href="#tests">Tests</a></li>
<li><a href="#style">Style</a>
<ul>
<li><a href="#git-commit-messages">Git Commit Messages</a></li>
<li><a href="#snippet-style">Snippet Style</a></li>
</ul>
</li>
</ul>
<a class="header" href="#getting-started" name="getting-started"><h2>Getting Started</h2></a>
<p>TODO: Mention Trello and how to join (if we keep using it)</p>
<a class="header" href="#how-to-contribute" name="how-to-contribute"><h2>How to Contribute</h2></a>
<p>TODO: Reporting bugs<br />
TODO: Project page suggestions<br />
TODO: Fixing bugs<br />
TODO: Pull requests</p>
<a class="header" href="#crates" name="crates"><h2>Crates</h2></a>
<p>TODO: How to add new crates to project</p>
<a class="header" href="#tests" name="tests"><h2>Tests</h2></a>
<p>TODO: Write about writing tests</p>
<a class="header" href="#style" name="style"><h2>Style</h2></a>
<p>https://aturon.github.io</p>
<a class="header" href="#git-commit-messages" name="git-commit-messages"><h3>Git Commit Messages</h3></a>
<p>https://chris.beams.io/posts/git-commit/<br />
TODO: Possibly take relevant parts from this post or write our own</p>
<a class="header" href="#snippet-style" name="snippet-style"><h3>Snippet Style</h3></a>
<p>TODO: Talk about writing good idiomatic code<br />
TODO: Maybe provide a template?</p>
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