I declared a template class threadBinaryTree and a function
void threadBinaryTree<T>::inThread
(threadBinaryTreeNode<T>*root,threadBinaryTreeNode<T>*& pre)
but complies error:
no matching function for call to ‘threadBinaryTree<char>::inThread
(threadBinaryTreeNode<char>*, NULL)’|
pre need to be initialized as NULL, how should I do?
Your second argument takes a non-const lvalue reference to some kind of pointer, but you are passing an rvalue (NULL). You cannot bind an rvalue to a non-const lvalue reference. You need to pass an lvalue:
threadBinaryTreeNode<T>* p = NULL;
x.inThread( somePtr, p );
The second argument is threadBinaryTreeNode<T>*& pre so you can not pass NULL to it.
threadBinaryTreeNode<T> *empty = 0; // Pass empty to the method instead of NULL
Also, it's better to use 0 and nullptr rather than NULL.
Since your second argument to your function is a non-const reference you need to supply a variable, something like this
threadBinaryTreeNode<char>* ptr = NULL;
inThread(..., ptr);
nullptr?NULLisn't c++ as far as I know.NULLis in C++ because it is in the C stdlib.nullptris preferred though because of better overload resolution behavior.