24 lines
679 B
Text
24 lines
679 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 init.data.nat.div init.coe
|
|
namespace Nat
|
|
|
|
def bitwise (f : Bool → Bool → Bool) : Nat → Nat → Nat | n m :=
|
|
if n = 0 then (if f ff tt then m else 0)
|
|
else if m = 0 then (if f tt ff then n else 0)
|
|
else
|
|
let n' := n / 2 in
|
|
let m' := m / 2 in
|
|
let b₁ := n % 2 = 1 in
|
|
let b₂ := m % 2 = 1 in
|
|
let r := bitwise n' m' in
|
|
if f b₁ b₂ then bit1 r else bit0 r
|
|
|
|
def land : Nat → Nat → Nat := bitwise band
|
|
def lor : Nat → Nat → Nat := bitwise bor
|
|
|
|
end Nat
|