/in/ex6.cpp: In function 'std::ostream& operator<<(std::ostream&, const BinaryTree&)':
/in/ex6.cpp:89:10: error: 'const class BinaryTree' has no member named 'traverse'
     tree.traverse(tree.root,os);
          ^~~~~~~~
/in/ex6.cpp: At global scope:
/in/ex6.cpp:93:54: error: no 'void BinaryTree::traverse(TreeNode*, std::ostream&) const' member function declared in class 'BinaryTree'
 void BinaryTree::traverse(TreeNode *root,ostream &os)const{
                                                      ^~~~~
/in/compile/Makefile:69: recipe for target 'ex6.o' failed
make: *** [ex6.o] Error 1