Past exam of the mathematics course of the University of Cambridge 2004 iii Paper 23 5 iv Solution Created 2026-10-03 Updated 2026-10-14
Every covariant representable functor preserves categorical limits, since a morphism out of into a limit is precisely a compatible cone. A filtered colimit of these functors is computed pointwise, and filtered colimits commute with finite limits in sets. Interchanging the finite limit and filtered colimit therefore proves that preserves finite limits, which is (i). This completes the cycle. It is also the flat functor and finite-limit preservation criterion for a finitely complete small category.