language: C++11 (gcc-4.7.2)
date: 169 days 20 hours ago
link:
visibility: private 
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#include <utility>
#include <iostream>
#include <memory>
 
 
template<class T>
struct moved_value{
    moved_value(T* v):pval(v){};
        
        T& get(){return *pval;}
        const T& get()const{return *pval;}
 
private:
        T* pval;
 
};
// Copied with removal of Parameter info from 
// http://stackoverflow.com/questions/7943525/is-it-possible-to-figure-out-the-parameter-type-and-return-type-of-a-lambda
 
 
template <typename T>
struct function_traits
    : public function_traits<decltype(&T::operator())>
{};
// For generic types, directly use the result of the signature of its 'operator()'
 
template <typename ClassType, typename ReturnType, typename... Args>
struct function_traits<ReturnType(ClassType::*)(Args...) const>
// we specialize for pointers to member function
{
    typedef ReturnType result_type;
 
};
 
template<class T,class F>
struct move_lambda{
        T val;
        F f_;
 
        typedef function_traits<F> traits;
        typedef typename traits::result_type result_type;
 
        
 
        move_lambda(T&& v, F f):val(std::move(v)),f_(f){};
        move_lambda(move_lambda&& other):val(std::move(other.val)),f_(std::move(other.f_)){}
 
        move_lambda& operator=(move_lambda&& other){
                val = std::move(other.val);
                f_ = std::move(other.f_);
 
        }
 
        template<class... Args>
        auto operator()(Args&& ...args) -> result_type
        {
            moved_value<T> mv(&val);
                return f_(mv,std::forward<Args>(args)...);
 
        }
 
 
 
private:
        move_lambda();
        move_lambda(const move_lambda&);
        move_lambda& operator=(const move_lambda&);
 
        
 
 
};
 
template<class T,class F>
move_lambda<T,F>create_move_lambda(T&& t, F f){
        return move_lambda<T,F>(std::move(t),f);
}
 
// Unfortunately, std::function does not seem to support move-only callables
// Here is our quick movable replacement
template< class ReturnType, class... ParamTypes>
struct movable_function_base{
        virtual ReturnType callFunc(ParamTypes&&... p) = 0;
 
};
 
 
template<class F, class ReturnType, class... ParamTypes>
struct movable_function_imp:public movable_function_base<ReturnType,ParamTypes...>{
                F f_;
        virtual ReturnType callFunc(ParamTypes&&... p){
                return f_(std::forward<ParamTypes>(p)...);
        }
 
        explicit movable_function_imp(F&& f):f_(std::move(f)){};
 
 
 
private:
        movable_function_imp();
        movable_function_imp(const movable_function_imp&);
        movable_function_imp& operator=(const movable_function_imp&);
};
 
 
template<class FuncType>
struct movable_function{};
 
template<class ReturnType, class... ParamTypes>
struct movable_function<ReturnType(ParamTypes...)>{
        std::unique_ptr<movable_function_base<ReturnType,ParamTypes...>> ptr_;
 
        template<class F>
        explicit movable_function(F&& f):ptr_(new movable_function_imp<F,ReturnType,ParamTypes...>(std::move(f))){}
        movable_function(movable_function&& other):ptr_(std::move(other.ptr_)){}
        movable_function& operator=(movable_function&& other){
                ptr_ = std::move(other.ptr_);
                return *this;
        }
 
        template<class... Args>
        auto operator()(Args&& ...args) -> ReturnType
        {
            return ptr_->callFunc(std::forward<Args>(args)...);
 
        }
private:
        movable_function();
        movable_function(const movable_function&);
        movable_function& operator=(const movable_function&);
 
};
 
 
 
 
struct TestMove{
        TestMove():k(0){}
        TestMove(TestMove&& other):k(other.k){
                other.k = -1;
        }
        TestMove& operator=(TestMove&& other){
                k = other.k;
                other.k = -1;
                return *this;
        }
 
        int k;
private:
        TestMove(const TestMove&);
        TestMove& operator=(const TestMove&);
 
 
};
 
movable_function<void()> CreateLambda()
 
{
   typedef TestMove HugeObject;
   HugeObject hugeObj;
   hugeObj.k = 9;
 
    // ...preparation of hugeObj...
 
 
   auto f = create_move_lambda(std::move(hugeObj),[](moved_value<HugeObject> hugeObj){// manipulate huge object
                std::cout << hugeObj.get().k << std::endl;
   
   });
 
  movable_function<void()> toReturn(std::move(f));
 
  return toReturn;
 
}
 
 
int main(){
 
        // A movable only type, not copyable
        TestMove m;
        m.k = 5;
 
        // A movable only type, not copyable
        TestMove m2;
        m2.k = 6;
        
        // Create a lambda that takes 2 parameters and returns int
        auto lambda = create_move_lambda(std::move(m),[](moved_value<TestMove> m,int i,int)->int{std::cout << m.get().k << " " << i << std::endl;return 7;});
        
        // Create a lambda that takes 0 parameters and returns void
        auto lambda2 = create_move_lambda(std::move(m2),[](moved_value<TestMove> m){std::cout << m.get().k << std::endl;});
 
 
        std::cout <<  lambda(1,2) << std::endl;
 
        lambda2();
 
 
        
 
        // Compiler error if you try to copy
        //auto lambda4 = lambda;
 
        // Able to move
        auto lambda3 = std::move(lambda2);
        lambda3();
 
        auto lambda4 = CreateLambda();
 
        lambda4();
 
}