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*All further definitions work for both constructions of the naturals.*

- Subsets of the natural numbers:

e.g.**N**_{>0}:= { `x`in**N**:`x`> 0};**N**_{n}:= { `x`in**N**:`x`<`n`}.**N**_{3}= {0, 1, 2}. *Predecessor*function:

e.g. 3`x`^{-}:=**such**`y`:`x`=`y`'.^{-}= 2; 0^{-}= ?.

Author: Wolfgang Schreiner

Last Modification: November 16, 1999