Bartosz Milewski on Nostr: Or, if you're a physicist, think of a profunctor as a mixed variance tensor ...

Or, if you're a physicist, think of a profunctor as a mixed variance tensor 𝑝ⁱₖ. Then a coend is just a trace of this tensor, 𝑝ⁱᵢ: \[ \int^i p i i \]