整理

include/boost/core/cmath.hpp

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+#ifndef BOOST_CORE_CMATH_HPP_INCLUDED
+#define BOOST_CORE_CMATH_HPP_INCLUDED
+
+// MS compatible compilers support #pragma once
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1020)
+# pragma once
+#endif
+
+// boost/core/cmath.hpp
+//
+// Floating point classification and sign manipulation functions
+// Extracted from https://github.com/boostorg/lexical_cast/pull/37
+//
+// Copyright 2020, 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <cmath>
+
+#if defined(BOOST_CORE_USE_GENERIC_CMATH) || (!defined(_MSC_VER) && !defined(FP_SUBNORMAL))
+
+#include <boost/core/detail/static_assert.hpp>
+#include <boost/cstdint.hpp>
+#include <limits>
+#include <cstring>
+
+namespace boost
+{
+namespace core
+{
+
+// fpclassify return values
+
+int const fp_zero = 0;
+int const fp_subnormal = 1;
+int const fp_normal = 2;
+int const fp_infinite = 3;
+int const fp_nan = 4;
+
+// Classification functions
+
+template<class T> bool isfinite( T x )
+{
+    return x <= (std::numeric_limits<T>::max)() && x >= -(std::numeric_limits<T>::max)();
+}
+
+template<class T> bool isinf( T x )
+{
+    return x > (std::numeric_limits<T>::max)() || x < -(std::numeric_limits<T>::max)();
+}
+
+template<class T> bool isnan( T x )
+{
+    return !isfinite( x ) && !isinf( x );
+}
+
+template<class T> bool isnormal( T x )
+{
+    return isfinite( x ) && ( x >= (std::numeric_limits<T>::min)() || x <= -(std::numeric_limits<T>::min)() );
+}
+
+template<class T> int fpclassify( T x )
+{
+    if( x == 0 ) return fp_zero;
+
+    if( x < 0 ) x = -x;
+
+    if( x > (std::numeric_limits<T>::max)() ) return fp_infinite;
+
+    if( x >= (std::numeric_limits<T>::min)() ) return fp_normal;
+
+    if( x < (std::numeric_limits<T>::min)() ) return fp_subnormal;
+
+    return fp_nan;
+}
+
+// Sign manipulation functions
+
+inline bool signbit( float x )
+{
+    boost::int32_t y;
+
+    BOOST_CORE_STATIC_ASSERT( sizeof( x ) == sizeof( y ) );
+
+    std::memcpy( &y, &x, sizeof( y ) );
+
+    return y < 0;
+}
+
+inline bool signbit( double x )
+{
+    boost::int64_t y;
+
+    BOOST_CORE_STATIC_ASSERT( sizeof( x ) == sizeof( y ) );
+
+    std::memcpy( &y, &x, sizeof( y ) );
+
+    return y < 0;
+}
+
+inline bool signbit( long double x )
+{
+    return signbit( static_cast<double>( x ) );
+}
+
+template<class T> T copysign( T x, T y )
+{
+    return signbit( x ) == signbit( y )? x: -x;
+}
+
+} // namespace core
+} // namespace boost
+
+#else // defined(BOOST_CORE_USE_GENERIC_CMATH)
+
+#if defined(_MSC_VER) && _MSC_VER < 1800
+# include <float.h>
+#endif
+
+namespace boost
+{
+namespace core
+{
+#if defined(_MSC_VER) && _MSC_VER < 1800
+
+template<class T> T copysign( T x, T y )
+{
+    return static_cast<T>( _copysign( static_cast<double>( x ), static_cast<double>( y ) ) );
+}
+
+template<class T> bool isnan( T x )
+{
+    return _isnan( static_cast<double>( x ) ) != 0;
+}
+
+template<class T> bool isfinite( T x )
+{
+    return _finite( static_cast<double>( x ) ) != 0;
+}
+
+template<class T> bool isinf( T x )
+{
+    return ( _fpclass( static_cast<double>( x ) ) & ( _FPCLASS_PINF | _FPCLASS_NINF ) ) != 0;
+}
+
+inline bool isnormal( float x )
+{
+    // no _fpclassf in 32 bit mode
+    unsigned y = reinterpret_cast< unsigned const& >( x );
+    unsigned exp = ( y >> 23 ) & 0xFF;
+    return exp != 0 && exp != 0xFF;
+}
+
+inline bool isnormal( double x )
+{
+    return ( _fpclass( x ) & ( _FPCLASS_PN | _FPCLASS_NN ) ) != 0;
+}
+
+inline bool isnormal( long double x )
+{
+    return boost::core::isnormal( static_cast<double>( x ) );
+}
+
+template<class T> bool signbit( T x )
+{
+    return _copysign( 1.0, static_cast<double>( x ) ) < 0.0;
+}
+
+int const fp_zero = 0;
+int const fp_subnormal = 1;
+int const fp_normal = 2;
+int const fp_infinite = 3;
+int const fp_nan = 4;
+
+inline int fpclassify( float x )
+{
+    switch( _fpclass( x ) )
+    {
+    case _FPCLASS_SNAN:
+    case _FPCLASS_QNAN:
+
+        return fp_nan;
+
+    case _FPCLASS_NINF:
+    case _FPCLASS_PINF:
+
+        return fp_infinite;
+
+    case _FPCLASS_NZ:
+    case _FPCLASS_PZ:
+
+        return fp_zero;
+
+    default:
+
+        return boost::core::isnormal( x )? fp_normal: fp_subnormal;
+    }
+}
+
+inline int fpclassify( double x )
+{
+    switch( _fpclass( x ) )
+    {
+    case _FPCLASS_SNAN:
+    case _FPCLASS_QNAN:
+
+        return fp_nan;
+
+    case _FPCLASS_NINF:
+    case _FPCLASS_PINF:
+
+        return fp_infinite;
+
+    case _FPCLASS_NZ:
+    case _FPCLASS_PZ:
+
+        return fp_zero;
+
+    case _FPCLASS_ND:
+    case _FPCLASS_PD:
+
+        return fp_subnormal;
+
+    default:
+
+        return fp_normal;
+    }
+}
+
+inline int fpclassify( long double x )
+{
+    return boost::core::fpclassify( static_cast<double>( x ) );
+}
+
+#else
+
+using std::isfinite;
+using std::isnan;
+using std::isinf;
+using std::isnormal;
+using std::fpclassify;
+
+int const fp_zero = FP_ZERO;
+int const fp_subnormal = FP_SUBNORMAL;
+int const fp_normal = FP_NORMAL;
+int const fp_infinite = FP_INFINITE;
+int const fp_nan = FP_NAN;
+
+using std::signbit;
+
+// std::copysign doesn't exist in libstdc++ under -std=c++03
+
+#if !defined(__GNUC__)
+
+template<class T> T copysign( T x, T y )
+{
+    return std::copysign( x, y );
+}
+
+#else
+
+namespace detail
+{
+
+// ::copysignl is unreliable, use the built-ins
+
+inline float copysign_impl( float x, float y )
+{
+    return __builtin_copysignf( x, y );
+}
+
+inline double copysign_impl( double x, double y )
+{
+    return __builtin_copysign( x, y );
+}
+
+inline long double copysign_impl( long double x, long double y )
+{
+    return __builtin_copysignl( x, y );
+}
+
+} // namespace detail
+
+template<class T> T copysign( T x, T y )
+{
+    return boost::core::detail::copysign_impl( x, y );
+}
+
+#endif // !defined(__GNUC__)
+#endif // #if defined(_MSC_VER) && _MSC_VER < 1800
+
+} // namespace core
+} // namespace boost
+
+#endif // defined(BOOST_CORE_USE_GENERIC_CMATH)
+
+#endif  // #ifndef BOOST_CORE_CMATH_HPP_INCLUDED