Request for CSE extraction Documentation/Offer to expand CSE extraction

[kylebd99]

I was looking at the extraction code, and it seems like it has a mechanism for common sub-expression handling. However, I couldn't quite tell what the strategy was for handling it. Would it be possible to expand the documentation on extract! to discuss this?

Also, I will likely need to handle CSE's in more detail for my project, and I could update the extraction code here if that's appropriate. At a first cut, I'm planning on following the integer linear programming approach outlined on page 10 of this paper.