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Definition df-bday 33049
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 33046 . 2 class bday
2 vx . . 3 setvar 𝑥
3 csur 33044 . . 3 class No
42cv 1527 . . . 4 class 𝑥
54cdm 5548 . . 3 class dom 𝑥
62, 3, 5cmpt 5137 . 2 class (𝑥 No ↦ dom 𝑥)
71, 6wceq 1528 1 wff bday = (𝑥 No ↦ dom 𝑥)
Colors of variables: wff setvar class
This definition is referenced by:  bdayval  33052  bdayfo  33079
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