to.hpp

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#pragma once
 
#include "indep/macro/overload.hpp"
#include "indep/helper/typeTrait.hpp"
#include <vector>
#include <type_traits>
 
namespace by {
 
    template <typename T, typename F> auto operator->*(T& t, F&& f) {
        if constexpr(std::is_reference_v<decltype(f(t))>) return &f(t);
        else return f(t);
    }
 
    template <typename T, typename F> auto operator->*(const T& t, F&& f) {
        if constexpr(std::is_reference_v<decltype(f(t))>) return &f(t);
        else return f(t);
    }
 
    template <typename T, typename F> auto operator->*(T&& t, F&& f) {
        if constexpr(std::is_reference_v<decltype(f(t))>) return &f(t);
        else return f(t);
    }
 
    template <typename T, typename F> auto operator->*(T* t, F&& f) {
        if constexpr(std::is_reference_v<decltype(f(*t))>) return t ? &f(*t) : typeTrait<decltype(&f(*t))>::ret();
        else return t ? f(*t) : typeTrait<decltype(f(*t))>::ret();
    }
 
    template <typename T, typename F> auto operator->*(const T* t, F&& f) {
        if constexpr(std::is_reference_v<decltype(f(*t))>) return t ? &f(*t) : typeTrait<decltype(&f(*t))>::ret();
        else return t ? f(*t) : typeTrait<decltype(f(*t))>::ret();
    }
 
 
#define TO(fn)                               \
    ->*[&](auto&& __p) -> decltype(__p.fn) { \
        return __p.fn;                       \
    }
 
} // namespace by