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Definition df-bday 27715
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  e.  No  |->  dom  x )

Detailed syntax breakdown of Definition df-bday
StepHypRef Expression
1 cbday 27712 . 2  class  bday
2 vx . . 3  setvar  x
3 csur 27710 . . 3  class  No
42cv 1363 . . . 4  class  x
54cdm 4836 . . 3  class  dom  x
62, 3, 5cmpt 4347 . 2  class  ( x  e.  No  |->  dom  x
)
71, 6wceq 1364 1  wff  bday  =  ( x  e.  No  |->  dom  x )
Colors of variables: wff setvar class
This definition is referenced by:  bdayval  27718  bdayfo  27745
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