On: Algebraic data types: things I wish someone had explained about FP (2019)

[bobbylarrybobby]

Yes, for the same reason that if you want to do logic, you'll need both the "and" and "or" operators; neither "and" nor "or" alone suffice.

[Hercuros → bobbylarrybobby]

This is not true for classical logic, because AND can be written using NOT and OR using DeMorgan's law.

[kd0amg → Hercuros]

OR alone is insufficient because you still need NOT (or AND and ⊥). You can also encode sum-like behavior using negation and products (a continuation consuming a pair of continuations).