Lean4
/-- The pull back of a complete sublattice under a complete lattice hom is a complete sublattice. -/
@[simps]
def comap (L : CompleteSublattice β) : CompleteSublattice α
where
carrier := f ⁻¹' L
supClosed' := L.supClosed.preimage f
infClosed' := L.infClosed.preimage f
sSupClosed' s
hs := by simpa only [mem_preimage, map_sSup, SetLike.mem_coe] using sSupClosed <| mapsTo_iff_image_subset.mp hs
sInfClosed' s
hs := by simpa only [mem_preimage, map_sInf, SetLike.mem_coe] using sInfClosed <| mapsTo_iff_image_subset.mp hs