expected constructor, destructor, or type conversion before & token

I'm getting a mysterious error in my project that says:

expected 开发者_如何学Goconstructor, destructor, or type conversion

It's not allowing me to use my overloaded operator<<. This previously worked before I made my class (myVector) into a template

//MyVector class
//An implementation of a vector of integers.
template <class T>
class MyVector{
public:
    //Purpose: Initialize an object of type MyVector
    //Parameters: none.
    //Returns: nothing.
    MyVector();

    //------------------------------------------------
    //Purpose: Initialize an object of type MyVector
    //Parameters: an integer.
    //Returns: nothing.
    //------------------------------------------------
    MyVector(int);

    //Purpose: Destroys objects of type MyVector
    //Parameters: none.
    //Returns: nothing
    //------------------------------------------------
    ~MyVector();

    //Purpose: Returns the current size of the MyVector.
    //Parameters: none.
    //Returns: the size.
    int size() const;

    //------------------------------------------------
    //Purpose: Returns the capacity of the MyVector.
    //Parameters: none.
    //Returns: int.
    int capacity() const;

    //------------------------------------------------
    //Purpose: Removes the entries of MyVector.
    //Parameters: none.
    //Returns: nothing.
    void clear();

    //------------------------------------------------
    //Purpose: Appends a given integer to the vector.
    //Parameters: an integer.
    //Returns: nothing.
    void push_back(T);

    //------------------------------------------------
    //Purpose: Shows what's at a given position.
    //Parameters: an integer index.
    //Returns: an integer.
    T at(int) const;

    MyVector(const MyVector& b);
    const MyVector& operator=(const MyVector&);

    //------------------------------------------------

private:
    int _size;
    int _capacity;
    int* head;

    //Purpose: Increases the capacity of a MyVector when it's 
    // capacity is equal to it's size. Called by push_back(int)
    //Parameters/Returns: nothing.
    void increase();

    //Purpose: Copies the given vector reference. 
    //Param: MyVector reference.
    //Returns: nothing.
    void copy(const MyVector&);

    //Purpose: Frees MyVector up for an assignment.
    void free();
};

template <class T>
ostream& operator<<(ostream&, const MyVector<T>);
//This line is giving me the error.

#endif

I have the code for the operator in a seperate file:

template <class T>
ostream& operator<<(ostream& os, const MyVector<T> V){
    int N = V.size();
    os << endl;
    for(int i = 0; i<N; i++){
        os << V.at(i)<<endl;
    }
    return os;
}

I've looked at other questions, but none seem to match mine. Help would be greatly appreciated. Thanks!

You probably need to qualify ostream with std as:

std::ostream& operator<<(std::ostream&, const MyVector<T>);

And you should almost certainly be passing your vector by const reference, rather than const value.

You can't declare a template in a file and then define it into another file. You can only define it.

Hope it helped you.

You should make the operator<< function accept a constant reference to the MyVector rather than just a constant, since what you are doing is to create a copy of the vector to pass into the function.

template <class T> std::ostream& operator<<(ostream& o, const MyVector<T>& V)

Expected constructor, destructor, or type conversion suggests that it does not recognize ostream as a type (ie, it has not been declared in this scope). Prefixing with std:: is not alone sufficient to resolve the issue; you must also include the dependent file.

#include <ostream> 

No need to Declare this:

template <class T>
ostream& operator<<(ostream&, const MyVector<T>);

You can follow this

#include <iostream>
using namespace std;
template <class T>
class A
{
public:
A();
int _size;
};
template <class T>
ostream& operator<<(ostream&, const A<T> p)
{
cout<<"in ostream"<<endl;
}
template <class T>
A<T>::A()
{
_size = 90;
cout<<_size<<endl;
}
int main()
{
A<int> ob;
cout<<ob;
return 0;
}