diff --git a/TinySTL/COWPtr.h b/TinySTL/COWPtr.h
index 8945646..fd23cfc 100644
--- a/TinySTL/COWPtr.h
+++ b/TinySTL/COWPtr.h
@@ -16,11 +16,31 @@ namespace TinySTL{
 		cow_ptr(const cow_ptr& cp);
 		cow_ptr& operator = (const cow_ptr& cp);
 
-		element_type operator *()const;
-		element_type *operator ->()const;
+		const element_type& operator *()const;
+		const element_type *operator ->()const;
+		//注意 这两个函数可能会改变指针指向的对象的内容，需要cow机制
+		//element_type& operator *();
+		//element_type *operator ->();
+
+		element_type *get();
+		const element_type *get()const;
+
+		operator bool() const;
 	private:
 		shared_ptr<element_type> ptr_;
-	
+	public:
+		template<class T1, class T2>
+		friend bool operator == (const cow_ptr<T1>& cp1, const cow_ptr<T2>& cp2);
+		template<class T>
+		friend bool operator == (const cow_ptr<T>& cp, nullptr_t p);
+		template<class T>
+		friend bool operator == (nullptr_t p, const cow_ptr<T>& cp);
+		template<class T1, class T2>
+		friend bool operator != (const cow_ptr<T1>& cp1, const cow_ptr<T2>& cp2);
+		template<class T>
+		friend bool operator != (const cow_ptr<T>& cp, nullptr_t p);
+		template<class T>
+		friend bool operator != (nullptr_t p, const cow_ptr<T>& cp);
 	};
 }
 
diff --git a/TinySTL/Detail/COWPtr.impl.h b/TinySTL/Detail/COWPtr.impl.h
index 69711f5..0010a1a 100644
--- a/TinySTL/Detail/COWPtr.impl.h
+++ b/TinySTL/Detail/COWPtr.impl.h
@@ -20,13 +20,55 @@ namespace TinySTL{
 		return *this;
 	}
 	template<class T>
-	typename cow_ptr<T>::element_type cow_ptr<T>::operator *()const{
+	const typename cow_ptr<T>::element_type& cow_ptr<T>::operator *()const{
 		return *ptr_;
 	}
 	template<class T>
-	typename cow_ptr<T>::element_type *cow_ptr<T>::operator ->()const{
+	const typename cow_ptr<T>::element_type *cow_ptr<T>::operator ->()const{
 		return ptr_.operator->();
 	}
+	//注意 这两个函数可能会改变指针指向的对象的内容，需要cow机制
+	//template<class T>
+	//typename cow_ptr<T>::element_type& cow_ptr<T>::operator *();
+	//template<class T>
+	//typename cow_ptr<T>::element_type *cow_ptr<T>::operator ->();
+	template<class T>
+	typename cow_ptr<T>::element_type *cow_ptr<T>::get(){
+		return ptr_.get();
+	}
+	template<class T>
+	const typename cow_ptr<T>::element_type *cow_ptr<T>::get()const{
+		return ptr_.get();
+	}
+	template<class T>
+	cow_ptr<T>::operator bool()const{
+		return ptr_ != nullptr;
+	}
+
+	template<class T1, class T2>
+	bool operator == (const cow_ptr<T1>& cp1, const cow_ptr<T2>& cp2){
+		return cp1.ptr_ == cp2.ptr_;
+	}
+	template<class T>
+	bool operator == (const cow_ptr<T>& cp, nullptr_t p){
+		return cp.ptr_ == p;
+	}
+	template<class T>
+	bool operator == (nullptr_t p, const cow_ptr<T>& cp){
+		return cp == p;
+	}
+	template<class T1, class T2>
+	bool operator != (const cow_ptr<T1>& cp1, const cow_ptr<T2>& cp2){
+		return !(cp1 == cp2);
+	}
+	template<class T>
+	bool operator != (const cow_ptr<T>& cp, nullptr_t p){
+		return !(cp == p);
+	}
+	template<class T>
+	bool operator != (nullptr_t p, const cow_ptr<T>& cp){
+		return !(cp == p);
+	}
 }
 
 #endif
\ No newline at end of file
diff --git a/TinySTL/Test/COWPtrTest.cpp b/TinySTL/Test/COWPtrTest.cpp
index f5cf347..139c1f4 100644
--- a/TinySTL/Test/COWPtrTest.cpp
+++ b/TinySTL/Test/COWPtrTest.cpp
@@ -7,14 +7,21 @@ namespace TinySTL{
 		void testCase1(){
 			cow_ptr<string> cp1(new string("hello"));
 			assert(*cp1 == "hello");
+			assert(cp1);
 			
-			cp1->append(" world");
 			auto cp2 = cp1;
-			assert(*cp2 == "hello world");
+			assert(*cp2 == "hello");
 
 			cow_ptr<string> cp3;
 			cp3 = cp1;
-			assert(*cp3 == "hello world");
+			assert(*cp3 == "hello");
+
+			assert(cp1.get() == cp2.get() && cp2.get() == cp3.get());
+
+			assert(cp1 == cp2 && !(cp2 != cp3));
+
+			cow_ptr<string> cp4;
+			assert(cp4 == nullptr);
 		}
 
 		void testAllCases(){