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Definition df-bday 33260
Description: Finally, we introduce the birthday function. This function maps each surreal to an ordinal. In our implementation, this is the domain of the sign function. The important properties of this function are established later. (Contributed by Scott Fenton, 11-Jun-2011.)
Assertion
Ref Expression
df-bday bday = (𝑥 No ↦ dom 𝑥)

Detailed syntax breakdown of Definition df-bday
StepHypRef Expression
1 cbday 33257 . 2 class bday
2 vx . . 3 setvar 𝑥
3 csur 33255 . . 3 class No
42cv 1537 . . . 4 class 𝑥
54cdm 5523 . . 3 class dom 𝑥
62, 3, 5cmpt 5113 . 2 class (𝑥 No ↦ dom 𝑥)
71, 6wceq 1538 1 wff bday = (𝑥 No ↦ dom 𝑥)
Colors of variables: wff setvar class
This definition is referenced by:  bdayval  33263  bdayfo  33290
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