View Compilation Error

0_0_9896504_23205.cpp: In member function `bool node::rol()':
0_0_9896504_23205.cpp:23: error: `null' undeclared (first use this function)
0_0_9896504_23205.cpp:23: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_9896504_23205.cpp: At global scope:
0_0_9896504_23205.cpp:36: error: `node null' used prior to declaration