C++实现的一个可以写递归lambda的Y函数

#include <functional>
#include <memory>
#include <iostream>
#include <string>

using namespace std;

template<typename TResult, typename ...TArgs>
class YBuilder
{

private:

  function<TResult(function<TResult(TArgs...)>, TArgs...)> partialLambda;

public:

  YBuilder(function<TResult(function<TResult(TArgs...)>, TArgs...)> _partialLambda)

    :partialLambda(_partialLambda)

  {

  }

  TResult operator()(TArgs ...args)const

  {

    return partialLambda(

      [this](TArgs ...args)

      {

        return this->operator()(args...);

      }, args...);

  }

};

template<typename TMethod>

struct PartialLambdaTypeRetriver

{

  typedef void FunctionType;

  typedef void LambdaType;

  typedef void YBuilderType;

};

template<typename TClass, typename TResult, typename ...TArgs>

struct PartialLambdaTypeRetriver<TResult(__thiscall TClass::*)(function<TResult(TArgs...)>, TArgs...)>
{

  typedef TResult FunctionType(TArgs...);

  typedef TResult LambdaType(function<TResult(TArgs...)>, TArgs...);

  typedef YBuilder<TResult, TArgs...> YBuilderType;

};


template<typename TClass, typename TResult, typename ...TArgs>

struct PartialLambdaTypeRetriver<TResult(__thiscall TClass::*)(function<TResult(TArgs...)>, TArgs...)const>

{

  typedef TResult FunctionType(TArgs...);

  typedef TResult LambdaType(function<TResult(TArgs...)>, TArgs...);

  typedef YBuilder<TResult, TArgs...> YBuilderType;

};

 

template<typename TLambda>

function<typename PartialLambdaTypeRetriver<decltype(&TLambda::operator())>::FunctionType> Y(TLambda partialLambda)

{

  return typename PartialLambdaTypeRetriver<decltype(&TLambda::operator())>::YBuilderType(partialLambda);

}

 

int _tmain(int argc, _TCHAR* argv[])

{

  auto fib = Y([](function<int(int)> self, int index)

  {

    return index<2

      ?1

      :self(index-1)+self(index-2);

  });

 

  for (int i = 0; i < 10; i++)
  {

    cout << fib(i) << " ";

  }

  cout << endl;

}