Rust提供原始类型到隐式类型之间的转换(强制)。但是，显式类型转换可以使用关键字as进行。
整数类型之间的转换规则遵循C约定, 除了在C是未定义行为的转换。所有类型转换整型的行为在Rust都很好的定义。
| fn main() { |
| let decimal = 65.4321_f32; |
| // Error! No implicit conversion |
| let integer: u8 = decimal; |
| // FIXME ^ Comment out this line |
| // Explicit conversion |
| let integer = decimal as u8; |
| let character = integer as char; |
| println!("Casting: {} -> {} -> {}", decimal, integer, character); |
| // when casting any value to an unsigned type, T, |
| // std::T::MAX + 1 is added or subtracted until the value |
| // fits into the new type |
| // 1000 already fits in a u16 |
| println!("1000 as a u16 is: {}", 1000 as u16); |
| // 1000 - 256 - 256 - 256 = 232 |
| println!("1000 as a u8 is : {}", 1000 as u8); |
| // -1 + 256 = 255 |
| println!(" -1 as a u8 is : {}", (-1i8) as u8); |
| // For positive numbers, this is the same as the modulus |
| println!("1000 mod 256 is : {}", 1000 % 256); |
| // When casting to a signed type, the result is the same as |
| // first casting to the corresponding unsigned type then |
| // taking the two's complement. |
| // Unless it already fits, of course. |
| println!(" 128 as a i16 is: {}", 128 as i16); |
| // 128 as u8 -> 128, whose two's complement in eight bits is: |
| println!(" 128 as a i8 is : {}", 128 as i8); |
| // repeating the example above |
| // 1000 as u8 -> 232 |
| println!("1000 as a i8 is : {}", 1000 as i8); |
| // and the two's complement of 232 is -24 |
| println!(" 232 as a i8 is : {}", 232 as i8); |
| } |
