Definition df-topn 12495

Description: Define the topology extractor function. This differs from df-tset 12412 when a structure has been restricted using df-ress 12339; in this case the TopSet component will still have a topology over the larger set, and this function fixes this by restricting the topology as well. (Contributed by Mario Carneiro, 13-Aug-2015.)

Assertion

Ref	Expression
df-topn	|- TopOpen = ( w e. _V |-> ( (TopSet ` w ) ↾t ( Base ` w ) ) )

Detailed syntax breakdown of Definition df-topn

Step	Hyp	Ref	Expression
1		ctopn 12493	. 2 class TopOpen
2		vw	. . 3 setvar w
3		cvv 2721	. . 3 class _V
4	2	cv 1341	. . . . 5 class w
5		cts 12399	. . . . 5 class TopSet
6	4, 5	cfv 5182	. . . 4 class (TopSet ` w )
7		cbs 12331	. . . . 5 class Base
8	4, 7	cfv 5182	. . . 4 class ( Base ` w )
9		crest 12492	. . . 4 class ↾t
10	6, 8, 9	co 5836	. . 3 class ( (TopSet ` w ) ↾t ( Base ` w ) )
11	2, 3, 10	cmpt 4037	. 2 class ( w e. _V |-> ( (TopSet ` w ) ↾t ( Base ` w ) ) )
12	1, 11	wceq 1342	1 wff TopOpen = ( w e. _V |-> ( (TopSet ` w ) ↾t ( Base ` w ) ) )

This definition is referenced by:  topnfn  12497  topnvalg  12504