View Compilation Error

0_0_19550603_28847.cpp: In member function 'const Node_ Node_::operator+(Node_&)':
0_0_19550603_28847.cpp:9:3: error: 'Node' was not declared in this scope
   Node nn;
   ^
0_0_19550603_28847.cpp:10:3: error: 'nn' was not declared in this scope
   nn.value=this->value+b.value;
   ^