Theorem bj-abf

Description: Shorter proof of abf (which should be kept as abfALT). (Contributed by BJ, 24-Jul-2019) (Proof modification is discouraged.)

	Ref	Expression
Hypothesis	bj-abf.1	|- -. ph
Assertion	bj-abf	|- { x | ph } = (/)

Proof

Step	Hyp	Ref	Expression
1		bj-abf.1	|- -. ph
2		bj-ab0	|- ( A. x -. ph -> { x | ph } = (/) )
3	2 1	mpg	|- { x | ph } = (/)