theorem znsubpos (m n: nat): $ n <= m -> m -ZN n = b0 (m - n) $;
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | lenlt | n <= m <-> ~m < n |
|
| 2 | ifneg | ~m < n -> if (m < n) (b1 (n - suc m)) (b0 (m - n)) = b0 (m - n) |
|
| 3 | 2 | conv znsub | ~m < n -> m -ZN n = b0 (m - n) |
| 4 | 1, 3 | sylbi | n <= m -> m -ZN n = b0 (m - n) |