150 lines
4.5 KiB
C++
150 lines
4.5 KiB
C++
///\file
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/******************************************************************************
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The MIT License(MIT)
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Embedded Template Library.
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https://github.com/ETLCPP/etl
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https://www.etlcpp.com
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Copyright(c) 2024 John Wellbelove
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files(the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions :
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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******************************************************************************/
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#ifndef ETL_GCD_INCLUDED
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#define ETL_GCD_INCLUDED
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#include "platform.h"
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#include "absolute.h"
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#include "static_assert.h"
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#include "type_traits.h"
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namespace etl
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{
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//***************************************************************************
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// Greatest Common Divisor.
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// Compile time.
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//***************************************************************************
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template <intmax_t Value1, intmax_t Value2>
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struct gcd_const
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{
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static ETL_CONSTANT intmax_t value = gcd_const<Value2, Value1 % Value2>::value;
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};
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template <intmax_t Value1>
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struct gcd_const<Value1, 0>
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{
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static ETL_CONSTANT intmax_t value = Value1;
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};
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//***************************************************************************
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// Greatest Common Divisor.
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// For unsigned types.
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//***************************************************************************
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template <typename T>
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ETL_NODISCARD ETL_CONSTEXPR14 typename etl::enable_if<etl::is_unsigned<T>::value, T>::type gcd(T a, T b) ETL_NOEXCEPT
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{
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ETL_STATIC_ASSERT(etl::is_integral<T>::value, "Integral type required");
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if ((a == 0 || b == 0))
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{
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return (a + b);
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}
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while (b != 0)
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{
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T t = b;
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b = a % b;
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a = t;
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}
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return a;
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}
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//***************************************************************************
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// Greatest Common Divisor.
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// For signed types.
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//***************************************************************************
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template <typename T>
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ETL_NODISCARD ETL_CONSTEXPR14 typename etl::enable_if<etl::is_signed<T>::value, T>::type gcd(T a, T b) ETL_NOEXCEPT
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{
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ETL_STATIC_ASSERT(etl::is_integral<T>::value, "Integral type required");
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typedef typename etl::make_unsigned<T>::type utype;
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utype ua = etl::absolute_unsigned(a);
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utype ub = etl::absolute_unsigned(b);
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return static_cast<T>(gcd(ua, ub));
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}
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#if ETL_USING_CPP11
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#if ETL_HAS_INITIALIZER_LIST
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//***************************************************************************
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// Greatest Common Divisor.
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// Non-recursive, using an initializer_list.
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// Top level variadic function.
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//***************************************************************************
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template <typename T, typename... TRest>
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ETL_NODISCARD ETL_CONSTEXPR14 T gcd(T first, TRest... rest) ETL_NOEXCEPT
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{
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T result = first;
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for (T value : {rest...})
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{
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result = gcd(result, value);
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if (result == 1)
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{
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// Early termination: if the GCD is one, it will remain one
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// no matter what other numbers are processed.
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return 1;
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}
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}
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return result;
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}
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#else
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//***************************************************************************
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// Greatest Common Divisor.
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// Recursive.
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// Top level variadic function.
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//***************************************************************************
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template <typename T, typename... TRest>
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ETL_NODISCARD ETL_CONSTEXPR14 T gcd(T a, T b, TRest... rest) ETL_NOEXCEPT
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{
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T gcd_ab = gcd(a, b);
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if (gcd_ab == 1)
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{
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// Early termination: if the GCD is one, it will remain one
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// no matter what other numbers are processed.
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return 1;
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}
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else
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{
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return gcd(gcd_ab, rest...);
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}
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}
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#endif
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#endif
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} // namespace etl
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#endif
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