Theorem nfab

Description: Bound-variable hypothesis builder for a class abstraction. (Contributed by Mario Carneiro, 11-Aug-2016) Add disjoint variable condition to avoid ax-13 . See nfabg for a less restrictive version requiring more axioms. (Revised by Gino Giotto, 20-Jan-2024)

	Ref	Expression
Hypothesis	nfab.1	|- F/ x ph
Assertion	nfab	|- F/_ x { y | ph }

Proof

Step	Hyp	Ref	Expression
1		nfab.1	|- F/ x ph
2	1	nfsab	|- F/ x z e. { y | ph }
3	2	nfci	|- F/_ x { y | ph }