26 lines
746 B
Text
26 lines
746 B
Text
/-
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Copyright (c) 2019 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Leonardo de Moura
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-/
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prelude
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import init.data.nat.basic init.data.nat.div init.coe
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namespace Nat
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partial def bitwise (f : Bool → Bool → Bool) : Nat → Nat → Nat | n m :=
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if n = 0 then (if f false true then m else 0)
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else if m = 0 then (if f true false then n else 0)
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else
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let n' := n / 2;
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let m' := m / 2;
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let b₁ := n % 2 = 1;
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let b₂ := m % 2 = 1;
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let r := bitwise n' m';
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if f b₁ b₂ then bit1 r else bit0 r
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@[extern cpp "lean::nat_land"]
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def land : Nat → Nat → Nat := bitwise and
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@[extern cpp "lean::nat_lor"]
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def lor : Nat → Nat → Nat := bitwise or
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end Nat
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