Primitive Types

Integers

• Signed integers: i8, i16, i32, i64, i128, isize
• Unsigned integers: u8, u16, u32, u64, u128, usize
• Integer literal 預設是 i32
• usize 用在索引 (indexing)

宣告整數的幾種方式：

let x: u8 = 10;
let y = 10u8;
let z = 100_000_000_i32;
let _ = 100_000__000___i32;

Floats

• f32, f64 (default)

  let my_float = 5.;
  

Characters

• One character (char) is 4 bytes. 底層是 u32。

  println!("Size of a char: {}", std::mem::size_of::<char>());
  

• u8 可以轉成 char

  let _x: u8 = 100;
  let _c = _x as char;
  

Strings

• 計算 string 佔幾 byte(s): .len()
• 計算 string 是幾個字元: .chars().count()
• .chars() 將 strings 轉成 collection of character。
• 將 string 以 collection of bytes 呈現: as_bytes()