[RESOLVED] Template Cast Operator. Possible?

I'm trying to do something in my code and it's giving me an error on compile. What I'm trying to do is put a template cast operator in a container class. Here's the simplified relevant code:

Code:

---

template<class T> class Container
{
public:
    template<class U> Container<U> operator U  (void)
    {
        // Convert each T element in 'list' to U elements in new Container, then return the container
    }
protected:
    std::vector<T> list;  // Contained objects
};

---

The operator method is actually defined in a separate file, if that matters.

Following is the GCC error given:
error: operator 'U' declared to return 'Container<U>'

I don't even know if this is possible. I need to know whether or not it is possible, and if so then how. What am I doing wrong? Otherwise, if anyone could come up with an alternative way to do this, I would greatly appreciate it. And if you're wondering, yes I have a good reason for wanting to do this. Thanks.

Type conversion functions like that one don't allow a return type to be specified. I'm not sure if it is possible myself, but I know that you can't specify a return type and that's most likely the reason for your error.

Oh, right! Yeah, I'm an idiot. It will build now, but I won't have a chance to test it for a while. Thanks

Edit:
Actually it will still mess up, as it will try to return a 'U' instead of a 'Container<U>'. I've fixed it and it should work now. Here is the modified code (just the operator):

Code:

---

    template<class U> operator Container<U>  (void)
    {
        // Convert each T element in 'list' to U elements in new Container, then return the container
    }

---

Again, I won't be able to test it, but it seems to work

Here is an example of a type conversion function:

Code:

---

template <typename Lo, typename Hi> Lo down_cast (const Hi& value)
{
    Lo result = Lo (a);
    if  (Hi (result) != value)
        throw exception ("loss of data in down cast");
    return result;
}

---

So in your case you might want to do something like this (untested) code:

Code:

---

template <typename Tout, typename Tin>
vector <Tout> ConvertStuff (const vector <Tin>& vIn)
{
    vector <Tout> vOut;

    for (int i = 0; i < vIn.size (); ++i)
    {
        Tout value = vIn [i];
        vOut.push_back (value);
    }
    return vOut;
}

---

As long as you have an assignment operator to convert the Tin to a Tout you should be okay.

You can use the copy constructor if type OutT has an assignment operator that accepts type InT instead of manual loops. Furthermore, it allows RVO.

Code:

---

template<typename InT, typename OutT>
vector<OutT> convert( const vector<InT>& op )
{
  return vector<OutT>( op.begin(), op.end() );
}

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