Definition df-riota 5971

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 5286. (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 5970	. 2 class (℩𝑥 ∈ 𝐴 𝜑)
5	2	cv 1396	. . . . 5 class 𝑥
6	5, 3	wcel 2202	. . . 4 wff 𝑥 ∈ 𝐴
7	6, 1	wa 104	. . 3 wff (𝑥 ∈ 𝐴 ∧ 𝜑)
8	7, 2	cio 5284	. 2 class (℩𝑥(𝑥 ∈ 𝐴 ∧ 𝜑))
9	4, 8	wceq 1397	1 wff (℩𝑥 ∈ 𝐴 𝜑) = (℩𝑥(𝑥 ∈ 𝐴 ∧ 𝜑))

This definition is referenced by:  riotaeqdv  5972  riotabidv  5973  riotaexg  5975  iotaexel  5976  riotav  5977  riotauni  5978  nfriota1  5979  nfriotadxy  5980  cbvriotavw  5982  cbvriota  5983  riotacl2  5986  riotabidva  5989  riota1  5991  riota2df  5993  snriota  6003  riotaund  6008  grpidvalg  13474  fn0g  13476  ismgmid  13478  oppr1g  14114  bdcriota  16529