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Definition df-bday 23710
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 23707 . 2  class  bday
2 vx . . 3  set  x
3 csur 23705 . . 3  class  No
42cv 1622 . . . 4  class  x
54cdm 4689 . . 3  class  dom  x
62, 3, 5cmpt 4077 . 2  class  ( x  e.  No  |->  dom  x
)
71, 6wceq 1623 1  wff  bday  =  ( x  e.  No  |->  dom  x )
Colors of variables: wff set class
This definition is referenced by:  bdayval  23713  bdayfo  23740
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