list3.cpp

#include <iostream>
#include <list>
#include <utility>

template<typename T>
std::ostream& operator<<(std::ostream& os,const std::list<T>& l)
{
  os<<"[";
  for(const auto& x:l)os<<x<<" ";
  os<<"]";
  return os;
}

template<typename T>
struct list:std::list<T>
{
  using base=std::list<T>;
  using base::base;
  list(const T& x):base(1,x){} // compatibility with mreturn
};

list<int> decinc(int x)
{
  return {x-1,x+1};
}

template<template<typename> class M,typename T>
M<T> mreturn(const T& x)
{
  return x;
}

template<typename T,typename F>
auto operator>>=(const list<T>& l, F f)
{
   decltype(f(std::declval<T>())) ret={};
   for(const auto& t:l)ret.splice(ret.end(),f(t));
   return std::move(ret);
}

template<template<typename> class M,typename T,typename F>
auto transform(const M<T>& m,F f)
{
  return m>>=[=](const auto& x){return mreturn<M>(f(x));};
}

int main()
{
  std::cout<<transform(list<int>{0,1,2},[](int x){return x+1;})<<"\n";
}