curry2.cpp

#include <type_traits>
#include <utility>
#include <tuple>

#include "function_traits.cpp"

template <typename Func, typename Env, typename Params, typename FuncParams>
struct closure;

template <typename Func, typename... Env, typename HeadFuncParams, typename... FuncParams>
struct closure<Func, std::tuple<Env...>, std::tuple<>, std::tuple<HeadFuncParams, FuncParams...>>
	: closure<Func, std::tuple<Env...>, std::tuple<HeadFuncParams>, std::tuple<FuncParams...>>
{
	using Base = closure<Func, std::tuple<Env...>, std::tuple<HeadFuncParams>, std::tuple<FuncParams...>>;
	
	using Base::Base;
	using Base::operator();
};

template <typename Func, typename... Env, typename HeadParams, typename... Params, typename HeadFuncParams, typename... FuncParams>
struct closure<Func, std::tuple<Env...>, std::tuple<HeadParams, Params...>, std::tuple<HeadFuncParams, FuncParams...>>
	: closure<Func, std::tuple<Env...>, std::tuple<HeadParams, Params..., HeadFuncParams>, std::tuple<FuncParams...>>
{
	using Base = closure<Func, std::tuple<Env...>, std::tuple<HeadParams, Params..., HeadFuncParams>, std::tuple<FuncParams...>>;
	
	using Base::Base;
	using Base::operator();
	
	constexpr
	auto operator()(HeadParams&& arg, Params&&... args) const& {
		return apply(std::make_index_sequence<sizeof...(Env)>{}, std::move(arg), std::move(args)...);
	}
	
	constexpr
	auto operator()(HeadParams&& arg, Params&&... args) && {
		return std::move(*this).apply(std::make_index_sequence<sizeof...(Env)>{}, std::move(arg), std::move(args)...);
	}
	
protected:
	template <size_t... Indices>
	constexpr
	auto apply(std::index_sequence<Indices...>, HeadParams&& arg, Params&&... args) const& {
		using NewEnv = std::tuple<Env..., HeadParams, Params...>;
		
		using NewClosure = closure<Func, NewEnv, std::tuple<>, std::tuple<HeadFuncParams, FuncParams...>>;
		
		return NewClosure{this->func, std::get<Indices>(this->env)..., std::move(arg), std::move(args)...};
	}
	
	template <size_t... Indices>
	constexpr
	auto apply(std::index_sequence<Indices...>, HeadParams&& arg, Params&&... args) && {
		using NewEnv = std::tuple<Env..., HeadParams, Params...>;
		
		using NewClosure = closure<Func, NewEnv, std::tuple<>, std::tuple<HeadFuncParams, FuncParams...>>;
		
		return NewClosure{std::move(this->func), std::get<Indices>(std::move(this->env))..., std::move(arg), std::move(args)...};
	}
};

template <typename Func, typename... Env, typename... Params>
struct closure<Func, std::tuple<Env...>, std::tuple<Params...>, std::tuple<>>
{
	constexpr
	closure(Func func, Env... args) :
		func(std::move(func)),
		env(std::forward<Env>(args)...)
	{ }
	
	constexpr
	auto operator()(Params&&... args) const& {
		return apply(std::make_index_sequence<sizeof...(Env)>{}, std::move(args)...);
	}
	
	constexpr
	auto operator()(Params&&... args) && {
		return std::move(*this).apply(std::make_index_sequence<sizeof...(Env)>{}, std::move(args)...);
	}
	
protected:
	template <size_t... Indices>
	constexpr
	auto apply(std::index_sequence<Indices...>, Params&&... args) const& {
		return func(std::get<Indices>(env)..., std::move(args)...);
	}
	
	template <size_t... Indices>
	constexpr
	auto apply(std::index_sequence<Indices...>, Params&&... args) && {
		return func(std::get<Indices>(std::move(env))..., std::move(args)...);
	}
	
	Func func;
	std::tuple<Env...> env;
};

template <typename Func>
auto curry(Func&& func) {
	using Closure = closure<Func, std::tuple<>, std::tuple<>, function_arg_tuple_t<Func>>;
	
	return Closure{ std::move(func) };
}