src/doc/nomicon/src/vec/vec-deref.md

   1 # Deref
   2
   3 Alright! We've got a decent minimal stack implemented. We can push, we can
   4 pop, and we can clean up after ourselves. However there's a whole mess of
   5 functionality we'd reasonably want. In particular, we have a proper array, but
   6 none of the slice functionality. That's actually pretty easy to solve: we can
   7 implement `Deref<Target=[T]>`. This will magically make our Vec coerce to, and
   8 behave like, a slice in all sorts of conditions.
   9
  10 All we need is `slice::from_raw_parts`. It will correctly handle empty slices
  11 for us. Later once we set up zero-sized type support it will also Just Work
  12 for those too.
  13
  14 <!-- ignore: simplified code -->
  15 ```rust,ignore
  16 use std::ops::Deref;
  17
  18 impl<T> Deref for Vec<T> {
  19     type Target = [T];
  20     fn deref(&self) -> &[T] {
  21         unsafe {
  22             std::slice::from_raw_parts(self.ptr.as_ptr(), self.len)
  23         }
  24     }
  25 }
  26 ```
  27
  28 And let's do DerefMut too:
  29
  30 <!-- ignore: simplified code -->
  31 ```rust,ignore
  32 use std::ops::DerefMut;
  33
  34 impl<T> DerefMut for Vec<T> {
  35     fn deref_mut(&mut self) -> &mut [T] {
  36         unsafe {
  37             std::slice::from_raw_parts_mut(self.ptr.as_ptr(), self.len)
  38         }
  39     }
  40 }
  41 ```
  42
  43 Now we have `len`, `first`, `last`, indexing, slicing, sorting, `iter`,
  44 `iter_mut`, and all other sorts of bells and whistles provided by slice. Sweet!