I am trying to define in Coq different types of equalities. During an university course my professor gave us the rules of four different types, as follows (I provide just the links to the rules):
- Gentzen : https://ibb.co/imQOCF
- Leibniz : https://ibb.co/n0uBzv
- Martin-Lof : https://ibb.co/fALZKv
- Path Induction : https://ibb.co/esZuKv
The difference among these four types relies on the type C.
I am trying to prove the isomorphism among them. Unfortunately I have some troubles in declaring as inductive types the first and the second, because I cannot find a way to specify the type C. I have a definition for the third and the fourth, and I already proved the isomorphism between them.
Thanks in advance.