My complete solutions to https://www.cis.upenn.edu/~cis194/spring13/
hw-gadt is an assignment on generalized algebraic data type and automated theorem proving based on lectures from https://www.seas.upenn.edu/~cis1940/spring15/lectures/10-gadts.html and https://www.seas.upenn.edu/~cis1940/spring15/lectures/11-stlc.html