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Definition df-bday 24370
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 24367 . 2  class  bday
2 vx . . 3  set  x
3 csur 24365 . . 3  class  No
42cv 1631 . . . 4  class  x
54cdm 4705 . . 3  class  dom  x
62, 3, 5cmpt 4093 . 2  class  ( x  e.  No  |->  dom  x
)
71, 6wceq 1632 1  wff  bday  =  ( x  e.  No  |->  dom  x )
Colors of variables: wff set class
This definition is referenced by:  bdayval  24373  bdayfo  24400
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