peak_ipl_interval.hpp

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#pragma once
 
#include <peak_ipl/backend/peak_ipl_attribute_defines.h>
#include <peak_ipl/exception/peak_ipl_exception.hpp>
#include <type_traits>
#include <cmath>
#include <limits>
#include <algorithm>

namespace peak
{
namespace ipl
{

template <typename T>
class Interval
{
public:
    constexpr Interval(T start, T end)
        : m_start{ start }
        , m_end{ end }
    {
        if (start > end)
        {
            throw InvalidArgumentException("start > end is not allowed!");
        }
        if (almostEqual(start, end))
        {
            throw InvalidArgumentException("start == end is not allowed!");
        }
    }

    PEAK_IPL_NO_DISCARD constexpr T Start() const
    {
        return m_start;
    }

    PEAK_IPL_NO_DISCARD constexpr T End() const
    {
        return m_end;
    }

    PEAK_IPL_NO_DISCARD constexpr bool InInterval(T value) const
    {
        return value >= m_start && value <= m_end;
    }
 
private:
    T m_start{}; 
    T m_end{}; 
 
    template <typename Q = T, std::enable_if_t<std::is_integral<Q>::value, int> = 0>
    static constexpr bool almostEqual(Q v1, Q v2)
    {
        return v1 == v2;
    }
 
    template <typename Q = T, std::enable_if_t<std::is_floating_point<Q>::value, int> = 0>
    static constexpr Q almostEqualMaxHelper(Q v1, Q v2)
    {
        return std::max<Q>({ 1.0, std::fabs(v1), std::fabs(v2) });
    }
 
    template <typename Q = T, std::enable_if_t<std::is_floating_point<Q>::value, int> = 0>
    static constexpr bool almostEqual(Q v1, Q v2)
    {
        return std::fabs(v1 - v2) <= std::numeric_limits<Q>::epsilon() * almostEqualMaxHelper(v1, v2);
    }
};
 
} /* namespace ipl */
} /* namespace peak */