When I draw a double line without arrow head, it produces \arrow[r, no head, Rightarrow] but compiling it with latex, I get a double line with head. It looks like the correct option is equal instead of no head, Rightarrow.

Pretty-print GATs as LaTeX in both of the following styles:

1. Cartmell-style linear notation

2. natural-deduction-style tree notation
   <img width="680" alt="image" src="https://user-images.githubusercontent.com/316610/91097121-f953b080-e613-11ea-8dda-8da598

Complete algorithm: http://web.cecs.pdx.edu/~mpj/pubs/polyrec.html

Do you intend to implement some of the functions Scott Wlaschin has in its AsyncResult/Result modules, e.g.

AsyncResult.catch
AsyncResult.ofAsync
AsyncResult.ofSuccess
AsyncResult.ofError
AsyncResult.ofResult?

https://github.com/swlaschin/DomainModelingMadeFunctional/blob/master/src/OrderTakingEvolved/Result.fs

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