Use methods rather than functions

[tmpfs]

The API feels a bit strange calling add_document_to_index(), remove_document_from_index() and vacuum_index() as they all accept &mut index as the first parameter.

Whilst we are making breaking changes I suggest using methods on Index:

impl Index {
  fn add_document(&mut self, ..) {}
  fn remove_document(&mut self, ..) {}
  fn vacuum(&mut self, ..) {}
}

I think this is more idiomatic. What do you think?

[marcus-pousette]

Yes you are right! At line 34 there is also already an impl for Index, so that makes a lot of sense! I think the reason for this, is that I was playing around with different memory layouts for the Index when building this library. There is a ghost_cell implementation that is about 30% more faster (if I remember correctly) in the ghost branch of this repo, where I think this, for some reason was justified. But I never succeeded to make the ghost_cell implementation compatible with WASM that requires you to be able to wrap the index with Mutex<...>.

In all, the change you suggest is preferred and is more idiomatic