| Description: Define the class of
converse reflexive relations. This is practically
dfcnvrefrels2 38529 (which uses the traditional subclass
relation ⊆) :
we use converse subset relation (brcnvssr 38507) here to ensure the
comparability to the definitions of the classes of all reflexive
(df-ref 23513), symmetric (df-syms 38543) and transitive (df-trs 38573) sets.
We use this concept to define functions (df-funsALTV 38682, df-funALTV 38683)
and disjoints (df-disjs 38705, df-disjALTV 38706).
For sets, being an element of the class of converse reflexive relations is
equivalent to satisfying the converse reflexive relation predicate, see
elcnvrefrelsrel 38537. Alternate definitions are dfcnvrefrels2 38529 and
dfcnvrefrels3 38530. (Contributed by Peter Mazsa,
7-Jul-2019.) |