Casting with character arrays

Code:

	template <typename OldType, typename NewType>
	any & change_type(any & operand)
	{
		try
		{
		any::placeholder * newcontent = new any::holder<NewType>(void_cast<NewType>(any_cast<OldType>(operand)));
		std::swap(operand.content,newcontent);
		delete newcontent;
		}
		catch (std::bad_cast)
		{
			cout << "TYPE1: " << typeid(OldType).name() << ' ' << "TYPE2: " << typeid(NewType).name() << endl;
			cout << "BOO HOO" << endl;
			return any::any();
		}
		cout << "TESTING" << endl;
		return operand;
	}

Using the catch, I finally figured out that the problem is that the any_cast isn't working. I then found out that the templates are not reading something like

change_type<int*,char*>(x);

as that, but as

change_type<int,char>(x);

which causes it to crash, because any_cast makes sure it returns the type that is currently stored in the any object.

Why isn't it taking the pointer?

One solution is function template overloading.

template <typename OldType, typename NewType>
any *& change_type(any *& operand)

template <typename OldType, typename NewType>
any * change_type(any * operand)

Kuphryn

I thought I tried that and it gave me problems... I'll try again

thx

Edit: Yeah, it didn't work. It can't convert any to any*...

That wasn't the problem though

The template seems to be discarding the pointer information, (int* is read as int), so its basically useless... If you try using a pointer, the program crashes.

Its basically the difference between

changetype<int*,char*>(x);

any::placeholder * newcontent = new any::holder<char*>(void_cast<char*>(any_cast<int*> (operand)));

and

changetype<int,char>(x);

any::placeholder * newcontent = new any::holder<char>(void_cast<char>(any_cast<int>(op erand)));

It never tries using char* or int*... it reads them as char and int, so it crashes with pointers.

I can't figure out why the templates aren't keeping all of the data!

It works if I change it to

Code:

	template <typename OldType, typename NewType>
	any & change_type(any & operand, OldType oldz, NewType newz)
	{
		try
		{
		any::placeholder * newcontent = new any::holder<NewType>(void_cast<NewType>(any_cast<OldType>(operand)));
		// any::placeholder * newcontent = new any::holder<NewType>(static_cast<NewType>(any_cast<OldType>(operand)));
		std::swap(operand.content,newcontent);
		delete newcontent;
		}
		catch (std::bad_cast)
		{
			cout << "TYPE1: " << typeid(OldType).name() << ' ' << "TYPE2: " << typeid(NewType).name() << endl;
			cout << "BAD CAST" << endl;
		}
		return operand;
	}

But that defeats the purpose because its terribly inconvenient to do this:

change_type(x,(int*)1,(char*)1);