memberfunctor.hpp

#ifndef SIPLASPLAS_UTILITY_MEMBERFUNCTOR_HPP
#define SIPALSPLAS_UTILITY_MEMBERFUNCTOR_HPP

#include "meta.hpp"
#include <utility>

namespace cpp
{

template<typename T>
using IsEboCandidate = ::cpp::meta::bool_<
    (sizeof(::cpp::meta::inherit<T, ::cpp::meta::aggregate<int>>) == sizeof(int))
>;

template<typename F, bool Ebo = IsEboCandidate<F>::value>
class MemberFunctor : private F
{
protected:
    template<typename... Args>
    constexpr MemberFunctor(Args&&... args) :
        F{std::forward<Args>(args)...}
    {}

    template<typename... Args>
    constexpr decltype(auto) invoke(Args&&... args) const
    {
        return F::operator()(std::forward<Args>(args)...);
    }

    template<typename... Args>
    constexpr decltype(auto) invoke(Args&&... args)
    {
        return F::operator()(std::forward<Args>(args)...);
    }

    constexpr const F& get() const
    {
        return *static_cast<const F*>(this);
    }

    constexpr F& get()
    {
        return *static_cast<F*>(this);
    }
};

template<typename F>
class MemberFunctor<F, false>
{
protected:
    template<typename... Args>
    constexpr MemberFunctor(Args&&... args) :
        _functor{std::forward<Args>(args)...}
    {}

    template<typename... Args>
    constexpr decltype(auto) invoke(Args&&... args) const
    {
        return _functor(std::forward<Args>(args)...);
    }

    template<typename... Args>
    constexpr decltype(auto) invoke(Args&&... args)
    {
        return _functor(std::forward<Args>(args)...);
    }

    constexpr const F& get() const
    {
        return _functor;
    }

    constexpr F& get()
    {
        return _functor;
    }

private:
    F _functor;
};

}

#endif // SIPLASPLAS_UTILITY_MEMBERFUNCTOR_HPP