complete lattice; closure operator; fixpoint; frame coproduct; compact frame
A constructively valid counterpart to Bourbaki's Fixpoint Lemma for chain-complete partially ordered sets is presented to obtain a condition for one closure system in a complete lattice $L$ to be stable under another closure operator of $L$. This is then used to deal with coproducts and other aspects of frames.
 Banaschewski B.: Another look at the localic Tychonoff Theorem
. Comment. Math. Univ. Carolinae 29 (1988), 647-656. MR 0982782
| Zbl 0667.54009
 Vermeulen J.J.C.: Some constructive results related to compactness and the (strong) Hausdorff property for locales
. preprint, 1991. MR 1173026
| Zbl 0739.18001