When borrows are involved, it is a common pattern to have a foo_mut variation of foo method. For example, [T] slices have a chunks method that takes &self and returns an iterator of &[T], and a chunks_mut method that is identical except that it takes &mut self and returns an iterator of &mut [T].

The windows method similarly takes &self and return an iterator of &[T]. However, the corresponding windows_mut does not exist, although it could sometimes be useful.