Dependent scope and nested templates

Question

When I compile this:

#ifndef BTREE_H
#define BTREE_H
#include 

template 
class btree
{
public:
    class node
    {
         


        

Answer 1

The C++ grammar is horrendous, and as such it is not possible, when given a template class, to know whether the ::node you refer to is a variable/constant or a type.

The Standard therefore mandates that you use typename before types to remove this ambiguity, and treats all other usages as if it was a variable.

Thus

template 
typename btree::node* btree::findLead(T const& value)
^~~~~~~~

is the correct signature for the definition.