Description: Define the class of
converse reflexive relations. This is practically
dfcnvrefrels2 35240 (which uses the traditional subclass
relation ⊆) :
we use converse subset relation (brcnvssr 35220) here to ensure the
comparability to the definitions of the classes of all reflexive
(df-ref 21829), symmetric (df-syms 35252) and transitive (df-trs 35282) sets.
We use this concept to define functions (df-funsALTV 35388, df-funALTV 35389)
and disjoints (df-disjs 35411, df-disjALTV 35412).
For sets, being an element of the class of converse reflexive relations is
equivalent to satisfying the converse reflexive relation predicate, see
elcnvrefrelsrel 35246. Alternate definitions are dfcnvrefrels2 35240 and
dfcnvrefrels3 35241. (Contributed by Peter Mazsa,
7-Jul-2019.) |