nan.h

// Description: Not-a-Number
// Documentation: numbers.txt

#ifndef PASTELSYS_NAN_H
#define PASTELSYS_NAN_H

#include "pastel/sys/sfinae.h"

#include <type_traits>
#include <limits>

#include <boost/operators.hpp>

namespace Pastel
{

    class Nan
    {
    public:
        template <
            typename Type,
            Requires<std::is_floating_point<Type>> = 0
        >
        operator Type() const
        {
            return std::numeric_limits<Type>::quiet_NaN();
        }

        template <
            typename Type,
            Requires<std::is_integral<Type>> = 0
        >
        operator Type() const
        {
            return std::numeric_limits<Type>::min();
        }

        template <
            typename Type,
            Requires<
                Or<
                    std::is_integral<Type>,
                    std::is_floating_point<Type>
                >
            > = 0
        >
        bool operator==(const Type& that) const
        {
            return that == (Type)*this;
        }

        template <typename Type>
        friend bool operator==(const Type& that, const Nan& nan)
        {
            return that != that;
        }

        template <
            typename Type,
            Requires<
                std::is_floating_point<Type>
            > = 0
        >
        bool operator!=(const Type& that) const
        {
            return !(that == *this);
        }

        template <typename Type>
        friend bool operator!=(const Type& that, const Nan& nan)
        {
            return nan != that;
        }
    };

    template <typename Type>
    bool isNan(const Type& that)
    {
        return that == Nan();
    }

}

#endif