Description: Define the orthocomplementation extractor for posets and related structures. (Contributed by NM, 4-Sep-2011) (Revised by Mario Carneiro, 14-Aug-2015) Use its index-independent form ocid instead. (New usage is discouraged.)
|- oc = Slot ; 1 1
|- oc
|- 1
|- ; 1 1
|- Slot ; 1 1