add zh/string.md
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@ -140,28 +140,10 @@ fn main() {
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}
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```
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🌟🌟 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.
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🌟🌟🌟 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.
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```rust,editable
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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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println!("{}", raw_str);
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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 longer_delimiter = r###"A string with "# in it. And even "##!"###;
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println!("{}", longer_delimiter);
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}
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```
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🌟🌟🌟
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```rust,editable
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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 below line to make it work
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@ -255,18 +237,6 @@ fn main() {
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}
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```
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🌟🌟
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```rust,editable
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use utf8_slice;
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fn main() {
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let s = "The 🚀 goes to the 🌑!";
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let rocket = utf8_slice::slice(s, 4, 5);
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}
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```
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#### utf8_slice
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You can use [utf8_slice](https://docs.rs/utf8_slice/1.0.0/utf8_slice/fn.slice.html) to slice UTF8 string, it can index chars instead of bytes.
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@ -1 +1,5 @@
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# Compound Types
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# 复合类型
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学习资料:
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- English: [Rust Book 4.3, 5.1, 6.1, 8.2](https://doc.rust-lang.org/book/ch04-03-slices.html)
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- 简体中文: [Rust语言圣经 - 复合类型](https://course.rs/basic/compound-type/intro.html)
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@ -1 +1,258 @@
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# string and slice
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# 字符串
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字符串字面量的类型是 `&str`， 例如 `let s: &str = "hello, world"` 中的 `"hello, world"` 的类型就是 `&str`。
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### `str` 和 `&str`
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🌟 正常情况下我们无法使用 `str` 类型，但是可以使用 `&str` 来替代
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```rust,editable
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// 修复错误，不要新增代码行
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fn main() {
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let s: str = "hello, world";
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}
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```
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🌟🌟🌟 如果要使用 `str` 类型，只能配合 `Box`。 `&` 可以用来将 `Box<str>` 转换为 `&str` 类型
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```rust,editable
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// 使用至少两种方法来修复错误
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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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}
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```
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### String
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`String` 是定义在标准库中的类型，分配在堆上，可以动态的增长。它的底层存储是动态字节数组的方式( `Vec<u8>` )，但是与字节数组不同，`String` 是 `UTF-8` 编码。
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🌟
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```rust,editable
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// 填空
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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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}
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```
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🌟🌟🌟
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```rust,editable
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// 修复所有错误，并且不要新增代码行
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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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}
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```
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🌟🌟 我们可以用 `replace` 方法来替换指定的子字符串
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```rust,editable
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// 填空
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fn main() {
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let s = String::from("I like dogs");
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// 以下方法会重新分配一块内存空间，然后将修改后的字符串存在这里
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let s1 = s.__("dogs", "cats");
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assert_eq!(s1, "I like cats")
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}
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```
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在标准库的 [String](https://doc.rust-lang.org/std/string/struct.String.html) 模块中，有更多的实用方法，感兴趣的同学可以看看。
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🌟🌟 你只能将 `String` 跟 `&str` 类型进行拼接，并且 `String` 的所有权在此过程中会被 move
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```rust,editable
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// 修复所有错误
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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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}
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```
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### `&str` 和 `String`
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与 `str` 的很少使用相比，`&str` 和 `String` 类型却非常常用，因此也非常重要。
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🌟🌟 我们可以使用两种方法将 `&str` 转换成 `String` 类型
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```rust,editable
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// 使用至少两种方法来修复错误
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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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}
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```
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🌟🌟 我们可以使用 `String::from` 或 `to_string` 将 `&str` 转换成 `String` 类型
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```rust,editable
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// 使用两种方法来解决错误，不要新增代码行
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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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}
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```
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### 字符串转义
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🌟
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```rust,editable
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fn main() {
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// 你可以使用转义的方式来输出想要的字符，这里我们使用十六进制的值，例如 \x73 会被转义成小写字母 's'
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// 填空以输出 "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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// 也可以使用 Unicode 形式的转义字符
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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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// 还能使用 \ 来连接多行字符串
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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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}
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```
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🌟🌟🌟 有时候需要转义的字符很多，我们会希望使用更方便的方式来书写字符串: raw string.
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```rust,editable
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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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// 修改以下代码行，让它工作
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assert_eq!(raw_str, "Escapes don't work here: ? ℝ");
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// 如果你希望在字符串中使用双引号，可以使用以下形式
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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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// 如果希望在字符串中使用 # 号，可以如下使用：
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let delimiter = r###"A string with "# in it. And even "##!"###;
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println!("{}", delimiter);
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// 填空
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let long_delimiter = __;
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assert_eq!(long_delimiter, "Hello, \"##\"")
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}
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```
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### 字节字符串
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想要一个非 UTF-8 形式的字符串吗(我们之前的 `str`, `&str`, `String` 都是 UTF-8 字符串) ? 可以试试字节字符串或者说字节数组:
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**示例**:
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```rust,editable
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use std::str;
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fn main() {
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// 注意，这并不是 `&str` 类型了！
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let bytestring: &[u8; 21] = b"this is a byte string";
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// 字节数组没有实现 `Display` 特征，因此只能使用 `Debug` 的方式去打印
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println!("A byte string: {:?}", bytestring);
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// 字节数组也可以使用转义
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let escaped = b"\x52\x75\x73\x74 as bytes";
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// ...但是不支持 unicode 转义
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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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// raw string
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let raw_bytestring = br"\u{211D} is not escaped here";
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println!("{:?}", raw_bytestring);
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// 将字节数组转成 `str` 类型可能会失败
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if let Ok(my_str) = str::from_utf8(raw_bytestring) {
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println!("And the same as text: '{}'", my_str);
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}
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let _quotes = br#"You can also use "fancier" formatting, \
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like with normal raw strings"#;
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// 字节数组可以不是 UTF-8 格式
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let shift_jis = b"\x82\xe6\x82\xa8\x82\xb1\x82\xbb"; // "ようこそ" in SHIFT-JIS
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// 但是它们未必能转换成 `str` 类型
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match str::from_utf8(shift_jis) {
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Ok(my_str) => println!("Conversion successful: '{}'", my_str),
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Err(e) => println!("Conversion failed: {:?}", e),
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};
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}
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```
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如果大家想要了解更多关于字符串字面量、转义字符的话，可以看看 Rust Reference 的 ['Tokens' 章节](https://doc.rust-lang.org/reference/tokens.html).
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### 字符串索引string index
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🌟🌟 你无法通过索引的方式去访问字符串中的某个字符，但是可以使用切片的方式 `&s1[start..end]` ，但是`start` 和 `end` 必须准确落在字符的边界处.
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```rust,editable
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fn main() {
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let s1 = String::from("hi,中国");
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let h = s1[0]; // 修改当前行来修复错误，提示: `h` 字符在 UTF-8 格式中只需要 1 个字节来表示
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assert_eq!(h, "h");
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let h1 = &s1[3..5];// 修改当前行来修复错误，提示: `中` 字符在 UTF-8 格式中需要 3 个字节来表示
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assert_eq!(h1, "中");
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}
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```
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### 操作 UTF-8 字符串
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🌟
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```rust,editable
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fn main() {
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// 填空，打印出 "你好，世界" 中的每一个字符
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for c in "你好，世界".__ {
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println!("{}", c)
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}
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}
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```
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#### utf8_slice
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我们可以使用三方库 [utf8_slice](https://docs.rs/utf8_slice/1.0.0/utf8_slice/fn.slice.html) 来访问 UTF-8 字符串的某个子串，但是与之前不同的是，该库索引的是字符，而不是字节.
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**Example**
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```rust
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use utf_slice;
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fn main() {
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let s = "The 🚀 goes to the 🌑!";
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let rocket = utf8_slice::slice(s, 4, 5);
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// 结果是 "🚀"
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}
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```
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