Calling Unsafe Functions
A function or method can be marked unsafe if it has extra preconditions you
must uphold to avoid undefined behaviour:
fn main() {let emojis = "🗻∈🌏";// Safe because the indices are in the correct order, within the bounds of// the string slice, and lie on UTF-8 sequence boundaries.unsafe {println!("{}", emojis.get_unchecked(0..4));println!("{}", emojis.get_unchecked(4..7));println!("{}", emojis.get_unchecked(7..11));}}