Rust practice

变量遮蔽 shadowing

fn type_of<T>(_: &T) -> String {
  format!("{}", std::any::type_name::<T>())
}

fn print<T: std::fmt::Display>(x: &T) {
  println!("{}\tsize({}): {}", type_of(x), std::mem::size_of_val(x), x);
}

fn main() {
  let x = 1u32 + 2;
  print(&x);

  // 变量遮蔽 shadowing
  let x = "hello world!";
  print(&x);
 
  // warning 常量需要大写
  // 常量不能被遮蔽 shadowing
  // 常量需要显式指定类型
  const Y: i32 = 12;
  let x = Y;
  print(&x);

  const Z: &str = "hello world!";
  let x = Z;
  print(&x)
}

Range

use std::ops::{Range, RangeInclusive};
fn main() {
    assert_eq!((1..5), Range{ start: 1, end: 5 });
    assert_eq!((1..=5), RangeInclusive::new(1, 5));
}

类型转换 as

fn main() {
    let v: u16 = 38u8 as u16;
}

数值类型

fn type_of<T>(_: &T) -> String {
  format!("{}", std::any::type_name::<T>())
}

fn print<T: std::fmt::Display>(x: &T) {
  println!("{}\tsize({}): {}", type_of(x), std::mem::size_of_val(x), x);
}

fn main() {
  let x = 1u32 + 2;
  print(&x);

  let x = 1i32 - 2;
  print(&x);
  
  let x = 1i8 - 2;
  print(&x);
  
  let x = 3 * 50;
  print(&x);
  
  let x = 9.6 / 3.2;
  print(&x);
  
  let x = 3 * 50;
  print(&x);
  
  let x = 24 % 5;
  print(&x);
  
  let x = true && false;
  print(&x);

  let x = true & false;
  print(&x);
}

字符，是Unicode编码，所有字符都是4个字节

fn type_of<T>(_: &T) -> String {
  format!("{}", std::any::type_name::<T>())
}

fn print<T: std::fmt::Display>(x: &T) {
  println!("{}\tsize({}): {}", type_of(x), std::mem::size_of_val(x), x);
}

fn main() {
  let x = 'a';
  print(&x);
  let x = '中';
  print(&x);
  let x = '😱';
  print(&x);
  let x = 'é';
  print(&x);
}