So much cocaine

#include <iostream>
#include <functional>
using namespace std;

typedef std::pair<bool, int>  li_t;
typedef std::function<li_t()> fi_t;

int main() {
    fi_t nil  = []() -> li_t {return std::make_pair(false, 0);};
    auto null = [](li_t a) -> bool {return !a.first;};
    auto val  = [](li_t a) -> int  {return a.second;};

    auto cons = [](int a, const fi_t& l) -> fi_t {
        int p=0; return [=]() mutable -> li_t {
                    if (p) return l(); else {p=1; return std::make_pair(true, a);}};};

    auto foldl = [cons,nil,null,val](const auto& f, auto a, const fi_t& l) -> fi_t {
        auto go = [f,cons,nil,null,val](auto a, const fi_t& l, const auto& la) -> fi_t {
            li_t e=l(); return null(e) ? a : la(f(val(e),a), l, la);};
        return go(a, l, go);};

    auto foldr = [cons,nil,null,val](const auto& f, auto a, const fi_t& l) -> fi_t {
        auto go = [f,cons,nil,null,val](auto a, const fi_t& l, const auto& la) -> fi_t {
            li_t e=l(); return null(e) ? a : f(val(e), la(a, l, la));};
        return go(a, l, go);};

    auto reverse = [cons,nil,foldl](const fi_t& l) -> fi_t {return foldl(cons, nil, l);};

    auto num2list = [cons, nil](int n, const auto& la) -> fi_t {
        return n ? cons(n%10, la(n/10, la)) : nil;};

    auto list2num = [cons,nil,val,foldr](const fi_t& l) -> int {
       auto go = [cons,nil,val](int a, const fi_t& l) -> fi_t {
            return cons(val(l())*10 + a,nil);};
       return val(foldr(go, nil, l)()); };

    int n; cout<<"Input n: "; cin>>n;
    cout<<"Inverse n = ";
    cout<<(list2num(reverse(num2list(n, num2list))))<<'\n';
    return 0;
}