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add carry_to_exp2

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bolero-MURAKAMI 2016-08-14 16:54:42 +09:00
parent 92c7169221
commit 0805756259
2 changed files with 76 additions and 0 deletions
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1
sprout/integer.hpp
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@ -10,6 +10,7 @@
#include <sprout/config.hpp>
#include <sprout/integer/integer_digits.hpp>
#include <sprout/integer/carry_to_exp2.hpp>
#include <sprout/integer/static_pow.hpp>
#endif // #ifndef SPROUT_INTEGER_HPP

75
sprout/integer/carry_to_exp2.hpp Normal file
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@ -0,0 +1,75 @@
/*=============================================================================
Copyright (c) 2011-2016 Bolero MURAKAMI
https://github.com/bolero-MURAKAMI/Sprout
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
=============================================================================*/
#ifndef SPROUT_INTEGER_CARRY_TO_EXP2_HPP
#define SPROUT_INTEGER_CARRY_TO_EXP2_HPP
#include <climits>
#include <limits>
#include <sprout/config.hpp>
#include <sprout/bit/cntl0.hpp>
#include <sprout/bit/popcount.hpp>
#include <sprout/type_traits/is_sint.hpp>
#include <sprout/type_traits/is_uint.hpp>
#include <sprout/type_traits/enabler_if.hpp>
namespace sprout {
namespace detail {
template<typename IntType>
inline SPROUT_CONSTEXPR IntType
carry_to_exp2_simpl(IntType x) {
return sprout::popcount(x) <= 1 ? x
: IntType(1) << (sizeof(IntType) * CHAR_BIT - sprout::cntl0(x))
;
}
template<typename UIntType>
inline SPROUT_CONSTEXPR UIntType
carry_to_exp2_uimpl(int n) {
return !n ? UIntType(0)
: UIntType(1) << (sizeof(UIntType) * CHAR_BIT - n)
;
}
} // namespace detail
//
// carry_to_exp2
//
// note: for signed integer
// x == MIN
// --> carry_to_exp2(x) returns x .
// x < 0
// --> carry_to_exp2(x) returns -carry_to_exp2(-x) .
// -(MIN / 2) < x
// --> carry_to_exp2(x) returns MIN .
//
// note: for unsigned integer
// MAX / 2 + 1 < x
// --> carry_to_exp2(x) returns 0 .
//
template<
typename IntType,
typename sprout::enabler_if<sprout::is_sint<IntType>::value>::type = sprout::enabler
>
inline SPROUT_CONSTEXPR IntType
carry_to_exp2(IntType x) {
return x == std::numeric_limits<IntType>::min() ? x
: x < IntType(0) ? -sprout::detail::carry_to_exp2_simpl(-x)
: sprout::detail::carry_to_exp2_simpl(x)
;
}
template<
typename UIntType,
typename sprout::enabler_if<sprout::is_uint<UIntType>::value>::type = sprout::enabler
>
inline SPROUT_CONSTEXPR UIntType
carry_to_exp2(UIntType x) {
return sprout::popcount(x) <= 1 ? x
: sprout::detail::carry_to_exp2_uimpl<UIntType>(sprout::cntl0(x))
;
}
} // namespace sprout
#endif // #ifndef SPROUT_INTEGER_CARRY_TO_EXP2_HPP