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<h1 id="string"><a class="header" href="#string">String</a></h1>
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<p>The type of string literal <code>"hello, world"</code> is <code>&str</code>, e.g <code>let s: &str = "hello, world"</code>.</p>
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<h3 id="str-and-str"><a class="header" href="#str-and-str">Str and &str</a></h3>
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<ol>
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<li>🌟 We can't use <code>str</code> type in normal ways, but we can use <code>&str</code>.</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// Fix error without adding new line
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fn main() {
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let s: str = "hello, world";
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println!("Success!");
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}</code></pre></pre>
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<ol start="2">
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<li>🌟🌟 We can only use <code>str</code> by boxing it, <code>&</code> can be used to convert <code>Box<str></code> to <code>&str</code></li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// Fix the error with at least two solutions
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fn main() {
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let s: Box<str> = "hello, world".into();
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greetings(s)
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}
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fn greetings(s: &str) {
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println!("{}",s)
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}</code></pre></pre>
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<h3 id="string-1"><a class="header" href="#string-1">String</a></h3>
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<p><code>String</code> type is defined in std and stored as a vector of bytes (Vec<u8>), but guaranteed to always be a valid UTF-8 sequence. String is heap allocated, growable and not null terminated.</p>
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<ol start="3">
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<li>🌟</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// Fill the blank
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fn main() {
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let mut s = __;
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s.push_str("hello, world");
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s.push('!');
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assert_eq!(s, "hello, world!");
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println!("Success!");
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}</code></pre></pre>
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<ol start="4">
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<li>🌟🌟🌟</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// Fix all errors without adding newline
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fn main() {
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let s = String::from("hello");
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s.push(',');
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s.push(" world");
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s += "!".to_string();
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println!("{}", s);
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}</code></pre></pre>
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<ol start="5">
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<li>🌟🌟 <code>replace</code> can be used to replace substring</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// Fill the blank
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fn main() {
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let s = String::from("I like dogs");
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// Allocate new memory and store the modified string there
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let s1 = s.__("dogs", "cats");
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assert_eq!(s1, "I like cats");
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println!("Success!");
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}</code></pre></pre>
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<p>More <code>String</code> methods can be found under <a href="https://doc.rust-lang.org/std/string/struct.String.html">String</a> module.</p>
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<ol start="6">
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<li>🌟🌟 You can only concat a <code>String</code> with <code>&str</code>, and <code>String</code>'s ownership can be moved to another variable.</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// Fix errors without removing any line
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fn main() {
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let s1 = String::from("hello,");
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let s2 = String::from("world!");
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let s3 = s1 + s2;
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assert_eq!(s3, "hello,world!");
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println!("{}", s1);
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}</code></pre></pre>
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<h3 id="str-and-string"><a class="header" href="#str-and-string">&str and String</a></h3>
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<p>Opposite to the seldom using of <code>str</code>, <code>&str</code> and <code>String</code> are used everywhere!</p>
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<ol start="7">
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<li>🌟🌟 <code>&str</code> can be converted to <code>String</code> in two ways</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// Fix error with at least two solutions
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fn main() {
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let s = "hello, world";
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greetings(s)
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}
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fn greetings(s: String) {
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println!("{}", s)
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}</code></pre></pre>
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<ol start="8">
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<li>🌟🌟 We can use <code>String::from</code> or <code>to_string</code> to convert a <code>&str</code> to <code>String</code></li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// Use two approaches to fix the error and without adding a new line
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fn main() {
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let s = "hello, world".to_string();
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let s1: &str = s;
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println!("Success!");
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}</code></pre></pre>
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<h3 id="string-escapes"><a class="header" href="#string-escapes">String escapes</a></h3>
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<ol start="9">
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<li>🌟</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">fn main() {
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// You can use escapes to write bytes by their hexadecimal values
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// Fill the blank below to show "I'm writing Rust"
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let byte_escape = "I'm writing Ru\x73__!";
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println!("What are you doing\x3F (\\x3F means ?) {}", byte_escape);
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// ...Or Unicode code points.
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let unicode_codepoint = "\u{211D}";
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let character_name = "\"DOUBLE-STRUCK CAPITAL R\"";
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println!("Unicode character {} (U+211D) is called {}",
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unicode_codepoint, character_name );
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let long_string = "String literals
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can span multiple lines.
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The linebreak and indentation here \
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can be escaped too!";
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println!("{}", long_string);
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}</code></pre></pre>
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<ol start="10">
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<li>🌟🌟🌟 Sometimes there are just too many characters that need to be escaped or it's just much more convenient to write a string out as-is. This is where raw string literals come into play.</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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/* Fill in the blank and fix the errors */
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fn main() {
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let raw_str = r"Escapes don't work here: \x3F \u{211D}";
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// Modify above line to make it work
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assert_eq!(raw_str, "Escapes don't work here: ? ℝ");
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// If you need quotes in a raw string, add a pair of #s
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let quotes = r#"And then I said: "There is no escape!""#;
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println!("{}", quotes);
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// If you need "# in your string, just use more #s in the delimiter.
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// You can use up to 65535 #s.
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let delimiter = r###"A string with "# in it. And even "##!"###;
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println!("{}", delimiter);
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// Fill the blank
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let long_delimiter = __;
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assert_eq!(long_delimiter, "Hello, \"##\"");
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println!("Success!");
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}</code></pre></pre>
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<h3 id="byte-string"><a class="header" href="#byte-string">Byte string</a></h3>
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<p>Want a string that's not UTF-8? (Remember, str and String must be valid UTF-8). Or maybe you want an array of bytes that's mostly text? Byte strings to the rescue!</p>
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<p><strong>Example</strong>:</p>
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||
<pre><pre class="playground"><code class="language-rust editable edition2021">use std::str;
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fn main() {
|
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// Note that this is not actually a `&str`
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let bytestring: &[u8; 21] = b"this is a byte string";
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|
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// Byte arrays don't have the `Display` trait, so printing them is a bit limited
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println!("A byte string: {:?}", bytestring);
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// Byte strings can have byte escapes...
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let escaped = b"\x52\x75\x73\x74 as bytes";
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// ...But no unicode escapes
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// let escaped = b"\u{211D} Is not allowed";
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println!("Some escaped bytes: {:?}", escaped);
|
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|
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|
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// Raw byte strings work just like raw strings
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let raw_bytestring = br"\u{211D} is not escaped here";
|
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println!("{:?}", raw_bytestring);
|
||
|
||
// Converting a byte array to `str` can fail
|
||
if let Ok(my_str) = str::from_utf8(raw_bytestring) {
|
||
println!("And the same as text: '{}'", my_str);
|
||
}
|
||
|
||
let _quotes = br#"You can also use "fancier" formatting, \
|
||
like with normal raw strings"#;
|
||
|
||
// Byte strings don't have to be UTF-8
|
||
let shift_jis = b"\x82\xe6\x82\xa8\x82\xb1\x82\xbb"; // "ようこそ" In SHIFT-JIS
|
||
|
||
// But then they can't always be converted to `str`
|
||
match str::from_utf8(shift_jis) {
|
||
Ok(my_str) => println!("Conversion successful: '{}'", my_str),
|
||
Err(e) => println!("Conversion failed: {:?}", e),
|
||
};
|
||
}</code></pre></pre>
|
||
<p>A more detailed listing of the ways to write string literals and escape characters is given in the <a href="https://doc.rust-lang.org/reference/tokens.html">'Tokens' chapter</a> of the Rust Reference.</p>
|
||
<h3 id="string-index"><a class="header" href="#string-index">String index</a></h3>
|
||
<ol start="11">
|
||
<li>🌟🌟🌟 You can't use index to access a char in a string, but you can use slice <code>&s1[start..end]</code>.</li>
|
||
</ol>
|
||
<pre><pre class="playground"><code class="language-rust editable edition2021">
|
||
fn main() {
|
||
let s1 = String::from("hi,中国");
|
||
let h = s1[0]; // Modify this line to fix the error, tips: `h` only takes 1 byte in UTF8 format
|
||
assert_eq!(h, "h");
|
||
|
||
let h1 = &s1[3..5]; // Modify this line to fix the error, tips: `中` takes 3 bytes in UTF8 format
|
||
assert_eq!(h1, "中");
|
||
|
||
println!("Success!");
|
||
}</code></pre></pre>
|
||
<h3 id="operate-on-utf8-string"><a class="header" href="#operate-on-utf8-string">Operate on UTF8 string</a></h3>
|
||
<ol start="12">
|
||
<li>🌟</li>
|
||
</ol>
|
||
<pre><pre class="playground"><code class="language-rust editable edition2021">
|
||
fn main() {
|
||
// Fill the blank to print each char in "你好，世界"
|
||
for c in "你好，世界".__ {
|
||
println!("{}", c)
|
||
}
|
||
}</code></pre></pre>
|
||
<h4 id="utf8_slice"><a class="header" href="#utf8_slice">utf8_slice</a></h4>
|
||
<p>You can use <a href="https://docs.rs/utf8_slice/1.0.0/utf8_slice/fn.slice.html">utf8_slice</a> to slice UTF8 string, it can index chars instead of bytes.</p>
|
||
<p><strong>Example</strong></p>
|
||
<pre><pre class="playground"><code class="language-rust edition2021">use utf8_slice;
|
||
fn main() {
|
||
let s = "The 🚀 goes to the 🌑!";
|
||
|
||
let rocket = utf8_slice::slice(s, 4, 5);
|
||
// Will equal "🚀"
|
||
}</code></pre></pre>
|
||
<blockquote>
|
||
<p>You can find the solutions <a href="https://github.com/sunface/rust-by-practice/blob/master/solutions/compound-types/string.md">here</a>(under the solutions path), but only use it when you need it</p>
|
||
</blockquote>
|
||
|
||
</main>
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