src/doc/unstable-book/src/advanced-slice-patterns.md

   1 # `advanced_slice_patterns`
   2
   3 The tracking issue for this feature is: [#23121]
   4
   5 [#23121]: https://github.com/rust-lang/rust/issues/23121
   6
   7 See also [`slice_patterns`](slice-patterns.html).
   8
   9 ------------------------
  10
  11
  12 The `advanced_slice_patterns` gate lets you use `..` to indicate any number of
  13 elements inside a pattern matching a slice. This wildcard can only be used once
  14 for a given array. If there's an identifier before the `..`, the result of the
  15 slice will be bound to that name. For example:
  16
  17 ```rust
  18 #![feature(advanced_slice_patterns, slice_patterns)]
  19
  20 fn is_symmetric(list: &[u32]) -> bool {
  21     match list {
  22         &[] | &[_] => true,
  23         &[x, ref inside.., y] if x == y => is_symmetric(inside),
  24         _ => false
  25     }
  26 }
  27
  28 fn main() {
  29     let sym = &[0, 1, 4, 2, 4, 1, 0];
  30     assert!(is_symmetric(sym));
  31
  32     let not_sym = &[0, 1, 7, 2, 4, 1, 0];
  33     assert!(!is_symmetric(not_sym));
  34 }
  35 ```