Summary:
We will use it inside `core` module, so we have to decouple it from `view`.
As part of this, I added some comments, changed `const Float &` to just `Float` and put the implementation into `.cpp` file.
Reviewed By: mdvacca
Differential Revision: D14593952
fbshipit-source-id: 80f7746f4fc5b95febc8df9f5a9c0386a6425c88
