34 lines
767 B
Text
34 lines
767 B
Text
/-
|
|
Copyright (c) 2019 Microsoft Corporation. All rights reserved.
|
|
Released under Apache 2.0 license as described in the file LICENSE.
|
|
Authors: Leonardo de Moura
|
|
-/
|
|
prelude
|
|
import Init.Data.Nat.Basic
|
|
import Init.Data.Nat.Div
|
|
import Init.Coe
|
|
|
|
namespace Nat
|
|
|
|
partial def bitwise (f : Bool → Bool → Bool) (n m : Nat) : Nat :=
|
|
if n = 0 then
|
|
if f false true then m else 0
|
|
else if m = 0 then
|
|
if f true false then n else 0
|
|
else
|
|
let n' := n / 2
|
|
let m' := m / 2
|
|
let b₁ := n % 2 = 1
|
|
let b₂ := m % 2 = 1
|
|
let r := bitwise f n' m'
|
|
if f b₁ b₂ then
|
|
r+r+1
|
|
else
|
|
r+r
|
|
|
|
@[extern "lean_nat_land"]
|
|
def land : Nat → Nat → Nat := bitwise and
|
|
@[extern "lean_nat_lor"]
|
|
def lor : Nat → Nat → Nat := bitwise or
|
|
|
|
end Nat
|