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<main>
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<h1 id="formatting"><a class="header" href="#formatting">Formatting</a></h1>
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<h2 id="positional-arguments"><a class="header" href="#positional-arguments">Positional arguments</a></h2>
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<p>1.🌟🌟</p>
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<pre><pre class="playground"><code class="language-rust editable edition2021">/* Fill in the blanks */
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fn main() {
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println!("{0}, this is {1}. {1}, this is {0}", "Alice", "Bob"); // => Alice, this is Bob. Bob, this is Alice
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assert_eq!(format!("{1}{0}", 1, 2), __);
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assert_eq!(format!(__, 1, 2), "2112");
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println!("Success!");
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}</code></pre></pre>
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<h2 id="named-arguments"><a class="header" href="#named-arguments">Named arguments</a></h2>
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<p>2.🌟🌟</p>
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<pre><pre class="playground"><code class="language-rust editable edition2021">fn main() {
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println!("{argument}", argument = "test"); // => "test"
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/* Fill in the blanks */
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assert_eq!(format!("{name}{}", 1, __), "21");
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assert_eq!(format!(__,a = "a", b = 'b', c = 3 ), "a 3 b");
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/* Fix the error */
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// Named argument must be placed after other arguments
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println!("{abc} {1}", abc = "def", 2);
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println!("Success!");
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}</code></pre></pre>
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<h2 id="padding-with-string"><a class="header" href="#padding-with-string">Padding with string</a></h2>
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<p>3.🌟🌟 By default, you can pad string with spaces</p>
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<pre><pre class="playground"><code class="language-rust editable edition2021">fn main() {
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// The following two are padding with 5 spaces
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println!("Hello {:5}!", "x"); // => "Hello x !"
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println!("Hello {:1$}!", "x", 5); // => "Hello x !"
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/* Fill in the blanks */
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assert_eq!(format!("Hello __!", 5, "x"), "Hello x !");
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assert_eq!(format!("Hello __!", "x", width = 5), "Hello x !");
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println!("Success!");
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}</code></pre></pre>
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<p>4.🌟🌟🌟 Left align, right align, pad with specified characters.</p>
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<pre><pre class="playground"><code class="language-rust editable edition2021">fn main() {
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// Left align
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println!("Hello {:<5}!", "x"); // => Hello x !
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// Right align
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assert_eq!(format!("Hello __!", "x"), "Hello x!");
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// Center align
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assert_eq!(format!("Hello __!", "x"), "Hello x !");
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// Left align, pad with '&'
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assert_eq!(format!("Hello {:&<5}!", "x"), __);
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println!("Success!");
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}</code></pre></pre>
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<p>5.🌟🌟 You can pad numbers with extra zeros.</p>
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<pre><pre class="playground"><code class="language-rust editable edition2021">fn main() {
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println!("Hello {:5}!", 5); // => Hello 5!
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println!("Hello {:+}!", 5); // => Hello +5!
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println!("Hello {:05}!", 5); // => Hello 00005!
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println!("Hello {:05}!", -5); // => Hello -0005!
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/* Fill in the blank */
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assert!(format!("{number:0>width$}", number=1, width=6) == __);
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println!("Success!")
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;}</code></pre></pre>
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<h2 id="precision"><a class="header" href="#precision">Precision</a></h2>
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<p>6.🌟🌟 Floating point precision</p>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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/* Fill in the blanks */
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fn main() {
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let v = 3.1415926;
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println!("{:.1$}", v, 4); // same as {:.4} => 3.1416
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assert_eq!(format!("__", v), "3.14");
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assert_eq!(format!("__", v), "+3.14");
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assert_eq!(format!("__", v), "3");
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println!("Success!");
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}</code></pre></pre>
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<p>7.🌟🌟🌟 String length</p>
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<pre><pre class="playground"><code class="language-rust editable edition2021">fn main() {
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let s = "Hello, world!";
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println!("{0:.5}", s); // => Hello
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assert_eq!(format!("Hello __!", 3, "abcdefg"), "Hello abc!");
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println!("Success!");
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}</code></pre></pre>
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<h2 id="binary-octal-hex"><a class="header" href="#binary-octal-hex">Binary, octal, hex</a></h2>
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<ul>
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<li>format!("{}", foo) -> "3735928559"</li>
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<li>format!("0x{:X}", foo) -> "0xDEADBEEF"</li>
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<li>format!("0o{:o}", foo) -> "0o33653337357"</li>
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</ul>
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<p>8.🌟🌟</p>
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<pre><pre class="playground"><code class="language-rust editable edition2021">fn main() {
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assert_eq!(format!("__", 27), "0b11011");
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assert_eq!(format!("__", 27), "0o33");
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assert_eq!(format!("__", 27), "0x1b");
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assert_eq!(format!("__", 27), "0x1B");
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println!("{:x}!", 27); // Hex with no prefix => 1b
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println!("{:#010b}", 27); // Pad binary with 0, width = 10, => 0b00011011
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println!("Success!");
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}</code></pre></pre>
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<h2 id="capture-the-environment"><a class="header" href="#capture-the-environment">Capture the environment</a></h2>
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<p>9.🌟🌟🌟</p>
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<pre><pre class="playground"><code class="language-rust editable edition2021">fn get_person() -> String {
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String::from("sunface")
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}
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fn get_format() -> (usize, usize) {
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(4, 1)
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}
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fn main() {
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let person = get_person();
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println!("Hello, {person}!");
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let (width, precision) = get_format();
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let scores = [("sunface", 99.12), ("jack", 60.34)];
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/* Make it print:
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sunface: 99.1
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jack: 60.3
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*/
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for (name, score) in scores {
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println!("{name}: __");
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}
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}</code></pre></pre>
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<h2 id="others"><a class="header" href="#others">Others</a></h2>
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<p><strong>Example</strong></p>
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<pre><pre class="playground"><code class="language-rust editable edition2021">fn main() {
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// Exponent
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println!("{:2e}", 1000000000); // => 1e9
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println!("{:2E}", 1000000000); // => 1E9
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// Pointer address
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let v= vec![1, 2, 3];
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println!("{:p}", v.as_ptr()); // => 0x600002324050
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// Escape
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println!("Hello {{}}"); // => Hello {}
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}</code></pre></pre>
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<blockquote>
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<p>You can find the solutions <a href="https://github.com/sunface/rust-by-practice/blob/master/solutions/formatted-output/formatting.md">here</a>(under the solutions path), but only use it when you need it :)</p>
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</blockquote>
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