Sat Nov 18 01:47:32 EST 2017

Product functor vs. sum functor

Interesting how sums keep appearing as "the other".  When thinking
about data types, I envision mostly products (structs), but sums are
just as important (unions).

Also in ada.  At the type level, the "or" looks "algebraic", while at
the proof / function level this requires case analysis.  Producs seem
that much simpler to express.

Where does the asymmetry come from, if these are really dual?