Borrowing and slices

The idea

Enter with ownership transfers understood. A shared reference borrows a value for reading without becoming its owner. A mutable reference permits mutation, but overlapping uses must obey Rust’s aliasing rules: either shared access or exclusive mutable access to the same place. The compiler checks the lifetimes during which references are actually used, so the end of a borrow need not be the closing brace.

Slices describe a borrowed contiguous portion of a sequence. An &[i32] parameter accepts arrays and vectors through borrowing without requiring a particular owning collection. An &str similarly borrows UTF-8 text. Indexing a Rust string by an integer is unavailable because a byte offset is not necessarily a character boundary. Match the interface to the information the helper needs.

fn total(values:&[i32])->i32 { values.iter().sum() }
fn main(){
 let mut values=vec![2,4,6];
 values[1]+=1;
 println!("{}",total(&values[1..]));
}

11

The slice borrows the last two elements, now five and six. The helper reads them without consuming the vector.