simple_composer.cpp

struct Comp
{
    template <class F1, class F2>
    auto operator()(F1 lhs, F2 rhs)
    {
        return [=](auto... args)
        {
            return lhs(rhs(args...));
            //     ^^^^^^^^^^^^^^^^^
        };
    }
};

template <class... Ts>
auto compose(Ts&&... args)
{
    using fld::Op;
    return (Op<Comp>(std::forward<Ts>(args)) + ...).give();
}