Utilities for the nested vector

If you think of using is crate, think again. Generally speaking, Vec<Vec<T>> is an antipattern because it is not contiguous -> not cache friendly -> slow. Nearly always, for the buffer you can and should use a newtype arround small_vec::SmallVec or Vec<T>, if possible. For example, if you have a dynamically-sized matrix, you should use the chosen contiguous buffer and maybe some data for dimensions.

However, if you believe that you have a legitimate use case for a nested vector, this crate provides a PoppingIterator, LendingIter, and LendingIterMut that you might want to use.

Example

use vec_vec::VecVecExt;

fn main() {
     let mut v = vec![vec![2, 3, 5], vec![], vec![7, 11, 13]];
     let mut iter = v.popping_iter();
    
     assert_eq!(iter.next(), Some(13));
     drop(iter);
     assert_eq!(v, vec![vec![2, 3, 5], vec![], vec![7, 11]]);
    
     let mut iter = v.popping_iter();
     assert_eq!(iter.next(), Some(11));
     assert_eq!(iter.container(), &vec![vec![2, 3, 5], vec![], vec![7]]);
    
     assert_eq!(iter.next(), Some(7));
     assert_eq!(iter.container(), &vec![vec![2, 3, 5], vec![], vec![]]);
    
     assert_eq!(iter.next(), Some(5));
     assert_eq!(iter.container(), &vec![vec![2, 3]]);
    
     assert_eq!(iter.next(), Some(3));
     assert_eq!(iter.container(), &vec![vec![2]]);
    
     assert_eq!(iter.next(), Some(2));
     assert_eq!(iter.container(), &vec![vec![]]);
    
     assert_eq!(iter.next(), None);
     assert_eq!(iter.container(), &Vec::<Vec<_>>::new());
}

Also see

• stack-trait for the stack trait with entry API, which is useful to avoid the limitations of the pre-Polonius NLL borrow checker.