Definition df-topn 13107

Description: Define the topology extractor function. This differs from df-tset 12961 when a structure has been restricted using df-iress 12873; 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 13105	. 2 class TopOpen
2		vw	. . 3 setvar w
3		cvv 2772	. . 3 class _V
4	2	cv 1372	. . . . 5 class w
5		cts 12948	. . . . 5 class TopSet
6	4, 5	cfv 5272	. . . 4 class (TopSet ` w )
7		cbs 12865	. . . . 5 class Base
8	4, 7	cfv 5272	. . . 4 class ( Base ` w )
9		crest 13104	. . . 4 class ↾t
10	6, 8, 9	co 5946	. . 3 class ( (TopSet ` w ) ↾t ( Base ` w ) )
11	2, 3, 10	cmpt 4106	. 2 class ( w e. _V |-> ( (TopSet ` w ) ↾t ( Base ` w ) ) )
12	1, 11	wceq 1373	1 wff TopOpen = ( w e. _V |-> ( (TopSet ` w ) ↾t ( Base ` w ) ) )

This definition is referenced by:  topnfn  13109  topnvalg  13116