use peekable_fwd_bwd::Peekable;
use core::slice::Iter;

let array = [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25];

const BWD_SIZE: usize = 2; // size of backward peek buffer.
const FWD_SIZE: usize = 8; // size of forward peek buffer.

let mut iter = Peekable::<Iter<i32>, BWD_SIZE, FWD_SIZE>::new(&array);

assert_eq!(iter.next(), Some(&10));
assert_eq!(iter.next(), Some(&11));

// forward peek into the future.
assert_eq!(iter.peek(), Some(&&12));
assert_eq!(iter.peek_nth(0), Some(&&12));
assert_eq!(iter.peek_nth(1), Some(&&13));
assert_eq!(iter.peek_nth(8), None); // FWD_SIZE too small.

assert_eq!(iter.next(), Some(&12));

// backward peek into the past.
assert_eq!(iter.peek_bwd(), Some(&&12));
assert_eq!(iter.peek_bwd_nth(0), Some(&&12));
assert_eq!(iter.peek_bwd_nth(1), Some(&&11));
assert_eq!(iter.peek_bwd_nth(2), None); // BWD_SIZE too small.