library/core/tests/iter/traits/double_ended.rs

   1 //! Note
   2 //! ----
   3 //! You're probably viewing this file because you're adding a test (or you might
   4 //! just be browsing, in that case, hey there!).
   5 //!
   6 //! If you've made a test that happens to use one of DoubleEnded's methods, but
   7 //! it tests another adapter or trait, you should *add it to the adapter or
   8 //! trait's test file*.
   9 //!
  10 //! Some examples would be `adapters::cloned::test_cloned_try_folds` or
  11 //! `adapters::flat_map::test_double_ended_flat_map`, which use `try_fold` and
  12 //! `next_back`, but test their own adapter.
  13
  14 #[test]
  15 fn test_iterator_rev_nth_back() {
  16     let v: &[_] = &[0, 1, 2, 3, 4];
  17     for i in 0..v.len() {
  18         assert_eq!(v.iter().rev().nth_back(i).unwrap(), &v[i]);
  19     }
  20     assert_eq!(v.iter().rev().nth_back(v.len()), None);
  21 }
  22
  23 #[test]
  24 fn test_iterator_rev_nth() {
  25     let v: &[_] = &[0, 1, 2, 3, 4];
  26     for i in 0..v.len() {
  27         assert_eq!(v.iter().rev().nth(i).unwrap(), &v[v.len() - 1 - i]);
  28     }
  29     assert_eq!(v.iter().rev().nth(v.len()), None);
  30 }
  31
  32 #[test]
  33 fn test_rev() {
  34     let xs = [2, 4, 6, 8, 10, 12, 14, 16];
  35     let mut it = xs.iter();
  36     it.next();
  37     it.next();
  38     assert!(it.rev().cloned().collect::<Vec<isize>>() == vec![16, 14, 12, 10, 8, 6]);
  39 }
  40
  41 #[test]
  42 fn test_rev_try_folds() {
  43     let f = &|acc, x| i32::checked_add(2 * acc, x);
  44     assert_eq!((1..10).rev().try_fold(7, f), (1..10).try_rfold(7, f));
  45     assert_eq!((1..10).rev().try_rfold(7, f), (1..10).try_fold(7, f));
  46
  47     let a = [10, 20, 30, 40, 100, 60, 70, 80, 90];
  48     let mut iter = a.iter().rev();
  49     assert_eq!(iter.try_fold(0_i8, |acc, &x| acc.checked_add(x)), None);
  50     assert_eq!(iter.next(), Some(&70));
  51     let mut iter = a.iter().rev();
  52     assert_eq!(iter.try_rfold(0_i8, |acc, &x| acc.checked_add(x)), None);
  53     assert_eq!(iter.next_back(), Some(&60));
  54 }
  55
  56 #[test]
  57 fn test_rposition() {
  58     fn f(xy: &(isize, char)) -> bool {
  59         let (_x, y) = *xy;
  60         y == 'b'
  61     }
  62     fn g(xy: &(isize, char)) -> bool {
  63         let (_x, y) = *xy;
  64         y == 'd'
  65     }
  66     let v = [(0, 'a'), (1, 'b'), (2, 'c'), (3, 'b')];
  67
  68     assert_eq!(v.iter().rposition(f), Some(3));
  69     assert!(v.iter().rposition(g).is_none());
  70 }
  71
  72 #[test]
  73 fn test_rev_rposition() {
  74     let v = [0, 0, 1, 1];
  75     assert_eq!(v.iter().rev().rposition(|&x| x == 1), Some(1));
  76 }
  77
  78 #[test]
  79 #[should_panic]
  80 fn test_rposition_panic() {
  81     let v: [(Box<_>, Box<_>); 4] = [(box 0, box 0), (box 0, box 0), (box 0, box 0), (box 0, box 0)];
  82     let mut i = 0;
  83     v.iter().rposition(|_elt| {
  84         if i == 2 {
  85             panic!()
  86         }
  87         i += 1;
  88         false
  89     });
  90 }