Path 2 to implement the State monad in C++ using Church Free

gistfile1.h

# This is an idea of how to merge the State monad and the Church Free monad
# without interferring with the inner eDSL.
# This code is incomplete and requires a further development.
# The idea is that we pass the state around with the Church Free functions
# as we would do it with a regular State monad.

# The overal concept is based on my Free monadic STM implementation:

# https://github.com/graninas/cpp_stm_free


#include <functional>
#include <variant>
#include <any>
#include <tuple>

using Any = std::any;

template <typename State>
using StateAny = std::tuple<State, Any>;

using Unit = int;

template <typename State, typename A, typename Next>
struct InnerLanguageMethod
{
    std::function<Next(Unit)> next;
};

template <typename State, typename Next>
using InnerLanguageMethodA = InnerLanguageMethod<State, Any, Next>;


template <typename State, class Ret>
struct STMF
{
    std::variant<
        InnerLanguageMethodA<State, Ret>
    > stmf;
};

template <typename State, typename A>
using StmlFunc = std::function<
        StateAny<State>(
            std::function<StateAny<State>(A)>,
            std::function<StateAny<State>(STMF<State, Any>)>
        )>;

template <typename State, typename A>
struct STML
{
    StmlFunc<State, A> runF;
};