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AK: Introduce IntegralMath.h starting with pow<I>

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Hendiadyoin1 2022-01-27 13:22:23 +01:00 committed by Brian Gianforcaro
parent 64f135d90f
commit 581c23dc55
Notes: sideshowbarker 2024-07-17 19:42:34 +09:00 
Author: https://github.com/Hendiadyoin1
Commit: https://github.com/SerenityOS/serenity/commit/581c23dc552
Pull-request: https://github.com/SerenityOS/serenity/pull/12163
Reviewed-by: https://github.com/BertalanD ✅
3 changed files with 56 additions and 0 deletions
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35
AK/IntegralMath.h Normal file
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@ -0,0 +1,35 @@
/*
* Copyright (c) 2022, Leon Albrecht <leon2002.la@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Concepts.h>
#include <AK/Types.h>
#include <AK/Format.h>
namespace AK {
template<Integral I>
constexpr I pow(I base, I exponent)
{
// https://en.wikipedia.org/wiki/Exponentiation_by_squaring
if (exponent < 0)
return 0;
if (exponent == 0)
return 1;
I res = 1;
while (exponent > 0) {
if (exponent & 1)
res *= base;
base *= base;
exponent /= 2u;
}
return res;
}
}

1
Tests/AK/CMakeLists.txt
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@ -33,6 +33,7 @@ set(AK_TEST_SOURCES
TestHex.cpp
TestIPv4Address.cpp
TestIndexSequence.cpp
TestIntegerMath.cpp
TestIntrusiveList.cpp
TestIntrusiveRedBlackTree.cpp
TestJSON.cpp

20
Tests/AK/TestIntegerMath.cpp Normal file
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@ -0,0 +1,20 @@
/*
* Copyright (c) 2022, the SerenityOS developers.
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibTest/TestCase.h>
#include <AK/IntegralMath.h>
TEST_CASE(pow)
{
EXPECT_EQ(AK::pow<u64>(10, 0), 1ull);
EXPECT_EQ(AK::pow<u64>(10, 1), 10ull);
EXPECT_EQ(AK::pow<u64>(10, 2), 100ull);
EXPECT_EQ(AK::pow<u64>(10, 3), 1'000ull);
EXPECT_EQ(AK::pow<u64>(10, 4), 10'000ull);
EXPECT_EQ(AK::pow<u64>(10, 5), 100'000ull);
EXPECT_EQ(AK::pow<u64>(10, 6), 1'000'000ull);
}