Definition df-riota 6041

Description: Define restricted description binder. In case there is no unique 𝑥 such that (𝑥 ∈ 𝐴 ∧ 𝜑) holds, it evaluates to the empty set. See also comments for df-iota 5340. (Contributed by NM, 15-Sep-2011.) (Revised by Mario Carneiro, 15-Oct-2016.) (Revised by NM, 2-Sep-2018.)

Assertion

Ref	Expression
df-riota	⊢ (℩𝑥 ∈ 𝐴 𝜑) = (℩𝑥(𝑥 ∈ 𝐴 ∧ 𝜑))

Detailed syntax breakdown of Definition df-riota

Step	Hyp	Ref	Expression
1		wph	. . 3 wff 𝜑
2		vx	. . 3 setvar 𝑥
3		cA	. . 3 class 𝐴
4	1, 2, 3	crio 6040	. 2 class (℩𝑥 ∈ 𝐴 𝜑)
5	2	cv 1401	. . . . 5 class 𝑥
6	5, 3	wcel 2209	. . . 4 wff 𝑥 ∈ 𝐴
7	6, 1	wa 104	. . 3 wff (𝑥 ∈ 𝐴 ∧ 𝜑)
8	7, 2	cio 5338	. 2 class (℩𝑥(𝑥 ∈ 𝐴 ∧ 𝜑))
9	4, 8	wceq 1402	1 wff (℩𝑥 ∈ 𝐴 𝜑) = (℩𝑥(𝑥 ∈ 𝐴 ∧ 𝜑))

This definition is used by:  riotaeqdv  6042  riotabidv  6043  riotaexg  6045  iotaexel  6046  riotav  6047  riotauni  6048  nfriota1  6049  nfriotadxy  6050  cbvriotavw  6052  cbvriota  6053  riotacl2  6056  riotabidva  6059  riota1  6061  riota2df  6063  snriota  6073  riotaund  6078  grpidvalg  13752  fn0g  13754  ismgmid  13756  oppr1g  14497  bdcriota  17114