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1 (* Title: ZF/Arith.thy |
1 (* Title: ZF/Arith.thy |
2 ID: $Id$ |
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3 Author: Lawrence C Paulson, Cambridge University Computer Laboratory |
2 Author: Lawrence C Paulson, Cambridge University Computer Laboratory |
4 Copyright 1992 University of Cambridge |
3 Copyright 1992 University of Cambridge |
5 |
|
6 *) |
4 *) |
7 |
5 |
8 (*"Difference" is subtraction of natural numbers. |
6 (*"Difference" is subtraction of natural numbers. |
9 There are no negative numbers; we have |
7 There are no negative numbers; we have |
10 m #- n = 0 iff m<=n and m #- n = succ(k) iff m>n. |
8 m #- n = 0 iff m<=n and m #- n = succ(k) iff m>n. |