Metamath Proof Explorer


Theorem nffun

Description: Bound-variable hypothesis builder for a function. (Contributed by NM, 30-Jan-2004)

Ref Expression
Hypothesis nffun.1
|- F/_ x F
Assertion nffun
|- F/ x Fun F

Proof

Step Hyp Ref Expression
1 nffun.1
 |-  F/_ x F
2 df-fun
 |-  ( Fun F <-> ( Rel F /\ ( F o. `' F ) C_ _I ) )
3 1 nfrel
 |-  F/ x Rel F
4 1 nfcnv
 |-  F/_ x `' F
5 1 4 nfco
 |-  F/_ x ( F o. `' F )
6 nfcv
 |-  F/_ x _I
7 5 6 nfss
 |-  F/ x ( F o. `' F ) C_ _I
8 3 7 nfan
 |-  F/ x ( Rel F /\ ( F o. `' F ) C_ _I )
9 2 8 nfxfr
 |-  F/ x Fun F