基本概念

Posted on June 18, 2020 本文总阅读量次

chapter 3 concepts

3.1 Variables 变量

mutable and immutable
variables and constants
shadowing

3.2 Data Types 数据类型

scalar 标量
integer: i8/i16/i32/i64/i128 u*
float-point: f32/f64
bool: true/false
character: char
compound 复合类型
tuple: let (x,y,z): (i32,f64,u8) = (2, 3.14, 4);
array: let a: [i32;5] = [3;5]; //[3,3,3,3,3]

3.3 Function 函数

1
2
3

fn fn_name(var:type,var2:type) -> ret_type {
	// statements
}

语句(statement): 是一些执行动作的指令，不会返回值。(statement are instructions that perform some action and do not return value)
表达式(expression): 运行计算一个值。(expression evaluate to a resulting value)

函数调用、宏(macro)调用、{}块都是一个表达式。
表达式不用分号结束，下面的例子，如果用分号结束，就变成了一个语句，不能正确编译。

let y = {
	let x=3;
	x+1
}

3.4 Comments 注释

// 单行注释
Rust have another kind comments, document comments, will discuss later.

/// 文档注释
//!

/* 块注释 */

3.5 Control flow流程控制

3.5.1 if语句

let num = 6;
if number % 4 == 0 {
	println!("number is divisible by 4");
} else if number % 3 == 0 {
	println!("number is divisible by 3");
} else {
	println!("number is not divisible by 4, 3.")
}

if is an expression

1	let num = if condition { 5 } else { 6 };

loop

let mut counter = 0;

let result = loop {
	counter += 1;

	if counter == 10 {
		break counter * 2;
	}
};

while

let mut number = 3;
while number != 0 {
	println!("{}!", number);

	number -= 1;
}

for

let a = [10, 20, 30, 40, 50];

for element in a.iter() {
	println!("the value is: {}", element);
}

for number in (1..4).rev() { // Range 1..4
	println!("{}!", number);
}