This is the first Homework. It will be graded and a grade will be assigned. This homework should not take more than a couple of hours.

In this homework you will construct a few Natural deduction style proofs using the code discussed in lecture. You will need the following 3 files.

You may want to study these files before you begin the homework. Your goal is to construct 5 terms of type NatDed, and run the checker to see that your terms are valid proofs of the following statements.- p /\ q |- q /\ p
- (p /\ q /\ r), (s /\ t) |- q /\ s
- p -> (q -> r), p -> q |- p -> r
- p1 -> p2, ~p2 |- ~p1
This rule schema is called modus Tollens

- p1 \/ ~p1
This is often called the rule if the excluded middle

Put all these functions into a file called Hw1.hs, check your proofs and submit it to D2L.