diff options
Diffstat (limited to 'Common/Nat.lean')
| -rw-r--r-- | Common/Nat.lean | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/Common/Nat.lean b/Common/Nat.lean index 3a605a9..9d0ee29 100644 --- a/Common/Nat.lean +++ b/Common/Nat.lean @@ -20,3 +20,6 @@ theorem lt_of_pred_lt {a b : Nat} (h₁ : a < b.pred) : (a < b) := match b with | 0 => h₁ | _ + 1 => /-(Nat.pred_succ a).substr $-/ Nat.lt_succ_of_lt h₁ + +theorem lt_imp_pred_lt {a b : Nat} (h₁ : a < b) : (a.pred < b) := + Nat.lt_of_le_of_lt (Nat.pred_le a) h₁ |