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Change bit_width to return int, LWG3656 has been applied as a DR to C++20

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Peter Dimov 2022-09-22 01:31:01 +03:00
parent 013c7856ce
commit b407b5d87d
2 changed files with 6 additions and 6 deletions
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4
doc/bit.qbk
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@ -45,7 +45,7 @@ template<class T>
constexpr T bit_floor(T x) noexcept; constexpr T bit_floor(T x) noexcept;
template<class T> template<class T>
constexpr T bit_width(T x) noexcept; constexpr int bit_width(T x) noexcept;
// Rotating // Rotating
@ -119,7 +119,7 @@ constant expression context.
* *Requires:* `T` must be an unsigned integer type. * *Requires:* `T` must be an unsigned integer type.
* *Returns:* If `x == 0`, 0; otherwise the maximal value `y` such that `has_single_bit(y)` is `true` and `y <= x`. * *Returns:* If `x == 0`, 0; otherwise the maximal value `y` such that `has_single_bit(y)` is `true` and `y <= x`.
`template<class T> constexpr T bit_width(T x) noexcept;` `template<class T> constexpr int bit_width(T x) noexcept;`
* *Requires:* `T` must be an unsigned integer type. * *Requires:* `T` must be an unsigned integer type.
* *Returns:* If `x == 0`, 0; otherwise one plus the base-2 logarithm of `x`, with any fractional part discarded. * *Returns:* If `x == 0`, 0; otherwise one plus the base-2 logarithm of `x`, with any fractional part discarded.

8
include/boost/core/bit.hpp
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@ -468,15 +468,15 @@ BOOST_CONSTEXPR bool has_single_bit( T x ) BOOST_NOEXCEPT
return x != 0 && ( x & ( x - 1 ) ) == 0; return x != 0 && ( x & ( x - 1 ) ) == 0;
} }
// bit_width should return int, https://cplusplus.github.io/LWG/issue3656 // bit_width returns `int` now, https://cplusplus.github.io/LWG/issue3656
// has been applied to C++20 as a DR
template<class T> template<class T>
BOOST_CONSTEXPR T bit_width( T x ) BOOST_NOEXCEPT BOOST_CONSTEXPR int bit_width( T x ) BOOST_NOEXCEPT
{ {
BOOST_STATIC_ASSERT( std::numeric_limits<T>::is_integer && !std::numeric_limits<T>::is_signed ); BOOST_STATIC_ASSERT( std::numeric_limits<T>::is_integer && !std::numeric_limits<T>::is_signed );
return static_cast<T>( return std::numeric_limits<T>::digits - boost::core::countl_zero( x );
std::numeric_limits<T>::digits - boost::core::countl_zero( x ) );
} }
template<class T> template<class T>