nextafter.hpp

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// SPDX-License-Identifier: BSL-1.0
// SPDX-FileCopyrightText: Copyright (C) 2021 Tobias Hienzsch
 
#ifndef TETL_CMATH_NEXTAFTER_HPP
#define TETL_CMATH_NEXTAFTER_HPP
 
#include <etl/_bit/bit_cast.hpp>
#include <etl/_cstdint/uint_t.hpp>
#include <etl/_type_traits/conditional.hpp>
#include <etl/_type_traits/is_same.hpp>
 
namespace etl {
 
namespace detail {
 
template <typename T>
[[nodiscard]] constexpr auto nextafter(T from, T to) -> T
{
    using U             = etl::conditional_t<sizeof(T) == 4U, etl::uint32_t, etl::uint64_t>;
    auto const fromBits = etl::bit_cast<U>(from);
    auto const toBits   = etl::bit_cast<U>(to);
    if (toBits == fromBits) {
        return to;
    }
    if (toBits > fromBits) {
        return etl::bit_cast<T>(fromBits + 1);
    }
    return etl::bit_cast<T>(fromBits - 1);
}
} // namespace detail
 
/// \ingroup cmath
/// @{
 
/// Returns the next representable value of from in the direction of to.
/// If from equals to, to is returned.
/// \details ttps://en.cppreference.com/w/cpp/numeric/math/nextafter
[[nodiscard]] constexpr auto nextafter(float from, float to) noexcept -> float
{
    return detail::nextafter(from, to);
}
[[nodiscard]] constexpr auto nextafterf(float from, float to) noexcept -> float
{
    return detail::nextafter(from, to);
}
[[nodiscard]] constexpr auto nextafter(double from, double to) noexcept -> double
{
    return detail::nextafter(from, to);
}
 
/// @}
 
} // namespace etl
 
#endif // TETL_CMATH_NEXTAFTER_HPP