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Diffstat (limited to 'backends/lean/Base/Arith/Base.lean')
| -rw-r--r-- | backends/lean/Base/Arith/Base.lean | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/backends/lean/Base/Arith/Base.lean b/backends/lean/Base/Arith/Base.lean index 9c11ed45..8ada4171 100644 --- a/backends/lean/Base/Arith/Base.lean +++ b/backends/lean/Base/Arith/Base.lean @@ -57,4 +57,16 @@ theorem int_pos_ind (p : Int → Prop) : -- TODO: there is probably something more general to do theorem nat_zero_eq_int_zero : (0 : Nat) = (0 : Int) := by simp +-- This is mostly used in termination proofs +theorem to_int_to_nat_lt (x y : ℤ) (h0 : 0 ≤ x) (h1 : x < y) : + ↑(x.toNat) < y := by + simp [*] + +-- This is mostly used in termination proofs +theorem to_int_sub_to_nat_lt (x y : ℤ) (x' : ℕ) + (h0 : ↑x' ≤ x) (h1 : x - ↑x' < y) : + ↑(x.toNat - x') < y := by + have : 0 ≤ x := by linarith + simp [Int.toNat_sub_of_le, *] + end Arith |