- Not every pair of elements has a difference in N:
- ~exists x: 0=x+1.
- x-y := such z: x = z+y.
- 0-1 is undefined.
- Introduce a set Z of integer numbers such that
- N can be "embedded" into Z, and
- for all integers a and b there is an integer x
with a = x+b (and consequently a-b is
Set-theoretic construction on top of N.
Author: Wolfgang Schreiner
Last Modification: November 16, 1999