15-317 Constructive Logic
Recitation 4: Arithmetic

Today's recitation focused on learning how to use Tutch to reason about natural numbers. We defined addition by structural recursion over its first argument and proved that adding anything to zero yields that same thing.

    val plus : nat -> nat -> nat
    proof plusN0N : !n:nat. plus n 0 = n
While proving this property of equality, we learned that Tutch employs a few somewhat subtle principles to generate proofs of equality. They are described in the handout for Assignment 3.


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Frank Pfenning