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81 lines
1.1 KiB
81 lines
1.1 KiB
# C-表达式
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在[语句与表达式]章节中，我们对表达式有过介绍，下面对这些常用表达式进行一一说明。
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### 基本表达式
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```rust
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let n = 3;
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let s = "test";
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```
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### if表达式
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```rust
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fn main() {
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let var1 = 10;
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let var2 = if var1 >= 10 {
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var1
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} else {
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var1 + 10
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};
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println!("{}", var2);
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}
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```
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通过`if`表达式将值赋予`var2`.
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你还可以在循环中结合`continue`、`break`来使用：`
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```rust
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let mut v = 0;
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for i in 1..10 {
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v = if i == 9 {
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continue
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} else {
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i
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}
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}
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println!("{}",v);
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```
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### if let表达式
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```rust
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let o = Some(3);
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let v = if let Some(x) = o {
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x
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} else {
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0
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};
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```
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### match表达式
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```rust
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let o = Some(3);
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let v = match o {
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Some(x) => x,
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_ => 0
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};
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```
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### loop表达式
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```rust
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let mut n = 0;
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let v = loop {
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if n == 10 {
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break n
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}
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n += 1;
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};
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```
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### 语句块{}
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```rust
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let mut n = 0;
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let v = {
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println!("before: {}", n);
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n += 1;
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println!("after: {}", n);
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n
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};
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println!("{}", v);
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``` |