Minor typo in section 2.5

[blakeelias]

In section 2.5, "Simplification and Rewriting", there is a minor typo. The sentence:

We may apply the defining equation to rewrite into a different formula, where we have essential pushed the definition of $\size{\cdot}$ through the $\mathsf{Plus}$.

should read:

We may apply the defining equation to rewrite into a different formula, where we have essentially pushed the definition of $\size{\cdot}$ through the $\mathsf{Plus}$.

[blakeelias]

(The word "essential" should be "essentially". Not sure how much you care about these types of issues for the moment, but anyway, here it is!)

[achlipala]

Thanks. I do indeed care about fixing that kind of typo. The version I post after class today will include this fix.