93 lines
2.1 KiB
Markdown
93 lines
2.1 KiB
Markdown
1.
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```rust
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fn main() {
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let decimal = 97.123_f32;
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let integer: u8 = decimal as u8;
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let c1: char = decimal as u8 as char;
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let c2 = integer as char;
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assert_eq!(integer, 'b' as u8 - 1);
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}
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```
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2.
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```rust
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// Suppress all warnings from casts which overflow.
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#![allow(overflowing_literals)]
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fn main() {
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assert_eq!(u8::MAX, 255);
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let v = 1000 as u8;
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}
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```
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3.
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```rust
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fn main() {
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assert_eq!(1000 as u16, 1000);
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assert_eq!(1000 as u8, 232);
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// For positive numbers, this is the same as the modulus
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println!("1000 mod 256 is : {}", 1000 % 256);
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assert_eq!(-1_i8 as u8, 255);
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// Since Rust 1.45, the `as` keyword performs a *saturating cast*
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// when casting from float to int. If the floating point value exceeds
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// the upper bound or is less than the lower bound, the returned value
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// will be equal to the bound crossed.
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assert_eq!(300.1_f32 as u8, 255);
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assert_eq!(-100.1_f32 as u8, 0);
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// This behavior incurs a small runtime cost and can be avoided
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// with unsafe methods, however the results might overflow and
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// return **unsound values**. Use these methods wisely:
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unsafe {
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// 300.0 is 44
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println!("300.0 is {}", 300.0_f32.to_int_unchecked::<u8>());
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// -100.0 as u8 is 156
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println!("-100.0 as u8 is {}", (-100.0_f32).to_int_unchecked::<u8>());
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// nan as u8 is 0
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println!("nan as u8 is {}", f32::NAN.to_int_unchecked::<u8>());
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}
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}
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```
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4.
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```rust
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fn main() {
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let mut values: [i32; 2] = [1, 2];
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let p1: *mut i32 = values.as_mut_ptr();
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let first_address = p1 as usize;
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let second_address = first_address + 4; // 4 == std::mem::size_of::<i32>()
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let p2 = second_address as *mut i32;
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unsafe {
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*p2 += 1;
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}
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assert_eq!(values[1], 3);
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println!("Success!")
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}
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```
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5.
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```rust
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fn main() {
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let arr :[u64; 13] = [0; 13];
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assert_eq!(std::mem::size_of_val(&arr), 8 * 13);
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let a: *const [u64] = &arr;
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let b = a as *const [u8];
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unsafe {
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assert_eq!(std::mem::size_of_val(&*b), 13)
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}
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}
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``` |