Metamath Proof Explorer


Definition df-refrels

Description: Define the class of reflexive relations. This is practically dfrefrels2 (which reveals that RefRels can not include proper classes like _I as is elements, see comments of dfrefrels2 ).

Another alternative definition is dfrefrels3 . The element of this class and the reflexive relation predicate ( df-refrel ) are the same, that is, ( R e. RefRels <-> RefRel R ) when A is a set, see elrefrelsrel .

This definition is similar to the definitions of the classes of symmetric ( df-symrels ) and transitive ( df-trrels ) relations. (Contributed by Peter Mazsa, 7-Jul-2019)

Ref Expression
Assertion df-refrels RefRels = ( Refs ∩ Rels )

Detailed syntax breakdown

Step Hyp Ref Expression
0 crefrels RefRels
1 crefs Refs
2 crels Rels
3 1 2 cin ( Refs ∩ Rels )
4 0 3 wceq RefRels = ( Refs ∩ Rels )