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Definition df-bday 27925
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 27922 . 2  class  bday
2 vx . . 3  setvar  x
3 csur 27920 . . 3  class  No
42cv 1369 . . . 4  class  x
54cdm 4943 . . 3  class  dom  x
62, 3, 5cmpt 4453 . 2  class  ( x  e.  No  |->  dom  x
)
71, 6wceq 1370 1  wff  bday  =  ( x  e.  No  |->  dom  x )
Colors of variables: wff setvar class
This definition is referenced by:  bdayval  27928  bdayfo  27955
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