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<ol class="chapter"><li class="chapter-item expanded "><a href="Chapter_0.html"><strong aria-hidden="true">1.</strong> Updates</a></li><li class="chapter-item expanded "><a href="Chapter_1.html"><strong aria-hidden="true">2.</strong> Introduction</a></li><li class="chapter-item expanded "><a href="Chapter_2.html"><strong aria-hidden="true">3.</strong> Who am I?</a></li><li class="chapter-item expanded "><a href="Chapter_3.html"><strong aria-hidden="true">4.</strong> Writing Rust in Easy English</a></li><li class="chapter-item expanded "><a href="Chapter_4.html"><strong aria-hidden="true">5.</strong> Rust Playground</a></li><li class="chapter-item expanded "><a href="Chapter_5.html"><strong aria-hidden="true">6.</strong> 🚧 and ⚠️</a></li><li class="chapter-item expanded "><a href="Chapter_6.html"><strong aria-hidden="true">7.</strong> Comments</a></li><li class="chapter-item expanded "><a href="Chapter_7.html"><strong aria-hidden="true">8.</strong> Types</a></li><li class="chapter-item expanded "><a href="Chapter_8.html"><strong aria-hidden="true">9.</strong> Type inference</a></li><li class="chapter-item expanded "><a href="Chapter_9.html"><strong aria-hidden="true">10.</strong> Printing 'hello, world!'</a></li><li class="chapter-item expanded "><a href="Chapter_10.html"><strong aria-hidden="true">11.</strong> Display and debug</a></li><li class="chapter-item expanded "><a href="Chapter_11.html"><strong aria-hidden="true">12.</strong> Mutability (changing)</a></li><li class="chapter-item expanded "><a href="Chapter_12.html"><strong aria-hidden="true">13.</strong> The stack, the heap, and pointers</a></li><li class="chapter-item expanded "><a href="Chapter_13.html"><strong aria-hidden="true">14.</strong> More about printing</a></li><li class="chapter-item expanded "><a href="Chapter_14.html"><strong aria-hidden="true">15.</strong> Strings</a></li><li class="chapter-item expanded "><a href="Chapter_15.html"><strong aria-hidden="true">16.</strong> const and static</a></li><li class="chapter-item expanded "><a href="Chapter_16.html"><strong aria-hidden="true">17.</strong> More on references</a></li><li class="chapter-item expanded "><a href="Chapter_17.html"><strong aria-hidden="true">18.</strong> Mutable references</a></li><li class="chapter-item expanded "><a href="Chapter_18.html"><strong aria-hidden="true">19.</strong> Giving references to functions</a></li><li class="chapter-item expanded "><a href="Chapter_19.html"><strong aria-hidden="true">20.</strong> Copy types</a></li><li class="chapter-item expanded "><a href="Chapter_20.html" class="active"><strong aria-hidden="true">21.</strong> Collection types</a></li><li class="chapter-item expanded "><a href="Chapter_21.html"><strong aria-hidden="true">22.</strong> Vectors</a></li><li class="chapter-item expanded "><a href="Chapter_22.html"><strong aria-hidden="true">23.</strong> Tuples</a></li><li class="chapter-item expanded "><a href="Chapter_23.html"><strong aria-hidden="true">24.</strong> Control flow</a></li><li class="chapter-item expanded "><a href="Chapter_24.html"><strong aria-hidden="true">25.</strong> Structs</a></li><li class="chapter-item expanded "><a href="Chapter_25.html"><strong aria-hidden="true">26.</strong> Enums</a></li><li class="chapter-item expanded "><a href="Chapter_26.html"><strong aria-hidden="true">27.</strong> Loops</a></li><li class="chapter-item expanded "><a href="Chapter_27.html"><strong aria-hidden="true">28.</strong> Implementing structs and enums</a></li><li class="chapter-item expanded "><a href="Chapter_28.html"><strong aria-hidden="true">29.</strong> Destructuring</a></li><li class="chapter-item expanded "><a href="Chapter_29.html"><strong aria-hidden="true">30.</strong> References and the dot operator</a></li><li class="chapter-item expanded "><a href="Chapter_30.html"><strong aria-hidden="true">31.</strong> Generics</a></li><li class="chapter-item expanded "><a href="Chapter_31.html"><strong aria-hidden="true">32.</strong> Option and Result</a></li><li class="chapter-item expanded "><a href="Chapter_32.html"><strong aria-hidden="true">33.</strong> Other collections</a></li><li class="chapter-item expanded "><a href="Chapter_33.html"><strong aria-hidden="true">34.</strong> The ? operator</a></li><li class="chapter-item expanded "><a href="Chapter_34.html"><strong aria-hidden="true">35.</strong> Traits</a></li><li class="chapter-item expanded "><a href="Chapter_35.html"><strong aria-hidden="true">36.</strong> Chaining methods</a></li><li class="chapter-item expanded "><a href="Chapter_36.html"><strong aria-hidden="true">37.</strong> Iterators</a></li><li class="chapter-item expanded "><a href="Chapter_37.html"><strong aria-hidden="true">38.</strong> Closures</a></li><li class="chapter-item expanded "><a href="Chapter_38.html"><strong aria-hidden="true">39.</strong> The dbg! macro and .inspect</a></li><li class="chapter-item expanded "><a href="Chapter_39.html"><strong aria-hidden="true">40.</strong> Types of &str</a></li><li class="chapter-item expanded "><a href="Chapter_40.html"><strong aria-hidden="true">41.</strong> Lifetimes</a></li><li class="chapter-item expanded "><a href="Chapter_41.html"><strong aria-hidden="true">42.</strong> Interior mutability</a></li><li class="chapter-item expanded "><a href="Chapter_42.html"><strong aria-hidden="true">43.</strong> Cow</a></li><li class="chapter-item expanded "><a href="Chapter_43.html"><strong aria-hidden="true">44.</strong> Type aliases</a></li><li class="chapter-item expanded "><a href="Chapter_44.html"><strong aria-hidden="true">45.</strong> The todo! macro</a></li><li class="chapter-item expanded "><a href="Chapter_45.html"><strong aria-hidden="true">46.</strong> Rc</a></li><li class="chapter-item expanded "><a href="Chapter_46.html"><strong aria-hidden="true">47.</strong> Multiple threads</a></li><li class="chapter-item expanded "><a href="Chapter_47.html"><strong aria-hidden="true">48.</strong> Closures in functions</a></li><li class="chapter-item expanded "><a href="Chapter_48.html"><strong aria-hidden="true">49.</strong> impl Trait</a></li><li class="chapter-item expanded "><a href="Chapter_49.html"><strong aria-hidden="true">50.</strong> Arc</a></li><li class="chapter-item expanded "><a href="Chapter_50.html"><strong aria-hidden="true">51.</strong> Channels</a></li><li class="chapter-item expanded "><a href="Chapter_51.html"><strong aria-hidden="true">52.</strong> Reading Rust documentation</a></li><li class="chapter-item expanded "><a href="Chapter_52.html"><strong aria-hidden="true">53.</strong> Attributes</a></li><li class="chapter-item expanded "><a href="Chapter_53.html"><strong aria-hidden="true">54.</strong> Box</a></li><li class="chapter-item expanded "><a href="Chapter_54.html"><strong aria-hidden="true">55.</strong> Box around traits</a></li><li class="chapter-item expanded "><a href="Chapter_55.html"><strong aria-hidden="true">56.</strong> Default and the builder pattern</a></li><li class="chapter-item expanded "><a href="Chapter_56.html"><strong aria-hidden="true">57.</strong> Deref and DerefMut</a></li><li class="chapter-item expanded "><a href="Chapter_57.html"><strong aria-hidden="true">58.</strong> Crates and modules</a></li><li class="chapter-item expanded "><a href="Chapter_58.html"><strong aria-hidden="true">59.</strong> Testing</a></li><li class="chapter-item expanded "><a href="Chapter_59.html"><strong aria-hidden="true">60.</strong> External crates</a></li><li class="chapter-item expanded "><a href="Chapter_60.html"><strong aria-hidden="true">61.</strong> A tour of the standard library</a></li><li class="chapter-item expanded "><a href="Chapter_61.html"><strong aria-hidden="true">62.</strong> Writing macros</a></li><li class="chapter-item expanded "><a href="Chapter_62.html"><strong aria-hidden="true">63.</strong> cargo</a></li><li class="chapter-item expanded "><a href="Chapter_63.html"><strong aria-hidden="true">64.</strong> Taking user input</a></li><li class="chapter-item expanded "><a href="Chapter_64.html"><strong aria-hidden="true">65.</strong> Using files</a></li><li class="chapter-item expanded "><a href="Chapter_65.html"><strong aria-hidden="true">66.</strong> cargo doc</a></li><li class="chapter-item expanded "><a href="Chapter_66.html"><strong aria-hidden="true">67.</strong> The end?</a></li></ol>
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<h1 class="menu-title">Easy Rust</h1>
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<main>
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<h2 id="collection-types"><a class="header" href="#collection-types">Collection types</a></h2>
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<p>Rust has a lot of types for making a collection. Collections are for when you need more than one value in one spot. For example, you could have information on all the cities in your country inside one variable. We will start with arrays, which are fastest but also have the least functionality. They are kind of like <code>&str</code> in that way.</p>
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<h3 id="arrays"><a class="header" href="#arrays">Arrays</a></h3>
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<p>An array is data inside square brackets: <code>[]</code>. Arrays:</p>
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<ul>
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<li>must not change their size,</li>
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<li>must only contain the same type.</li>
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</ul>
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<p>They are very fast, however.</p>
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<p>The type of an array is: <code>[type; number]</code>. For example, the type of <code>["One", "Two"]</code> is <code>[&str; 2]</code>. This means that even these two arrays have different types:</p>
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<pre><pre class="playground"><code class="language-rust">fn main() {
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let array1 = ["One", "Two"]; // This one is type [&str; 2]
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let array2 = ["One", "Two", "Five"]; // But this one is type [&str; 3]. Different type!
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}
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</code></pre></pre>
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<p>Here is a good tip: to know the type of a variable, you can "ask" the compiler by giving it bad instructions. For example:</p>
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<pre><pre class="playground"><code class="language-rust">fn main() {
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let seasons = ["Spring", "Summer", "Autumn", "Winter"];
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let seasons2 = ["Spring", "Summer", "Fall", "Autumn", "Winter"];
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seasons.ddd(); // ⚠️
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seasons2.thd(); // ⚠️ as well
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}
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</code></pre></pre>
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<p>The compiler says, "What? There's no <code>.ddd()</code> method for seasons and no <code>.thd()</code> method for seasons 2 either!!" as you can see:</p>
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<pre><code class="language-text">error[E0599]: no method named `ddd` found for array `[&str; 4]` in the current scope
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--> src\main.rs:4:13
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4 | seasons.ddd(); //
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| ^^^ method not found in `[&str; 4]`
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error[E0599]: no method named `thd` found for array `[&str; 5]` in the current scope
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--> src\main.rs:5:14
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5 | seasons2.thd(); //
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| ^^^ method not found in `[&str; 5]`
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</code></pre>
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<p>So it tells you <code>method not found in `[&str; 4]`</code>, which is the type.</p>
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<p>If you want an array with all the same value, you can declare it like this:</p>
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<pre><pre class="playground"><code class="language-rust">fn main() {
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let my_array = ["a"; 10];
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println!("{:?}", my_array);
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}
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</code></pre></pre>
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<p>This prints <code>["a", "a", "a", "a", "a", "a", "a", "a", "a", "a"]</code>.</p>
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<p>This method is used a lot to create buffers. For example, <code>let mut buffer = [0; 640]</code> creates an array of 640 zeroes. Then we can change zero to other numbers in order to add data.</p>
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<p>You can index (get) entries in an array with []. The first entry is [0], the second is [1], and so on.</p>
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<pre><pre class="playground"><code class="language-rust">fn main() {
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let my_numbers = [0, 10, -20];
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println!("{}", my_numbers[1]); // prints 10
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}
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</code></pre></pre>
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<p>You can get a slice (a piece) of an array. First you need a &, because the compiler doesn't know the size. Then you can use <code>..</code> to show the range.</p>
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<p>For example, let's use this array: <code>[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]</code>.</p>
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<pre><pre class="playground"><code class="language-rust">fn main() {
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let array_of_ten = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
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let three_to_five = &array_of_ten[2..5];
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let start_at_two = &array_of_ten[1..];
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let end_at_five = &array_of_ten[..5];
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let everything = &array_of_ten[..];
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println!("Three to five: {:?}, start at two: {:?}, end at five: {:?}, everything: {:?}", three_to_five, start_at_two, end_at_five, everything);
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}
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</code></pre></pre>
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<p>Remember that:</p>
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<ul>
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<li>Index numbers start at 0 (not 1)</li>
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<li>Index ranges are <strong>exclusive</strong> (they do not include the last number)</li>
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</ul>
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<p>So <code>[0..2]</code> means the first index and the second index (0 and 1). Or you can call it the "zeroth and first" index. It doesn't have the third item, which is index 2.</p>
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<p>You can also have an <strong>inclusive</strong> range, which means it includes the last number too. To do this, add <code>=</code> to write <code>..=</code> instead of <code>..</code>. So instead of <code>[0..2]</code> you can write <code>[0..=2]</code> if you want the first, second, and third item.</p>
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<script src="book.js" type="text/javascript" charset="utf-8"></script>
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</body>
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