mathlib

a2d7b55a - feat(order/complete_boolean_algebra): Frames (#11709)

feat(order/complete_boolean_algebra): Frames (#11709) Define the order theoretic `order.frame` and `order.coframe` and insert them between `complete_lattice` and `complete_distrib_lattice`. Co-authored-by: Yury G. Kudryashov <urkud@urkud.name>