Definition df-undef 8060

Description: Define the undefined value function, whose value at set 𝑠 is guaranteed not to be a member of 𝑠 (see pwuninel 8062). (Contributed by NM, 15-Sep-2011.)

Assertion

Ref	Expression
df-undef	⊢ Undef = (𝑠 ∈ V ↦ 𝒫 ∪ 𝑠)

Detailed syntax breakdown of Definition df-undef

Step	Hyp	Ref	Expression
1		cund 8059	. 2 class Undef
2		vs	. . 3 setvar 𝑠
3		cvv 3422	. . 3 class V
4	2	cv 1538	. . . . 5 class 𝑠
5	4	cuni 4836	. . . 4 class ∪ 𝑠
6	5	cpw 4530	. . 3 class 𝒫 ∪ 𝑠
7	2, 3, 6	cmpt 5153	. 2 class (𝑠 ∈ V ↦ 𝒫 ∪ 𝑠)
8	1, 7	wceq 1539	1 wff Undef = (𝑠 ∈ V ↦ 𝒫 ∪ 𝑠)

This definition is referenced by:  undefval  8063