Metamath Proof Explorer

Theorem nfiota

Description: Bound-variable hypothesis builder for the iota class. Usage of this theorem is discouraged because it depends on ax-13 . Use the weaker nfiotaw when possible. (Contributed by NM, 23-Aug-2011) (New usage is discouraged.)

Ref Expression
Hypothesis nfiota.1 x φ
Assertion nfiota _ x ι y | φ


Step Hyp Ref Expression
1 nfiota.1 x φ
2 nftru y
3 1 a1i x φ
4 2 3 nfiotad _ x ι y | φ
5 4 mptru _ x ι y | φ