View Compilation Error

0_0_37311479_23895.cpp: In function 'bool com(node, node)':
0_0_37311479_23895.cpp:26:12: error: 'a' was not declared in this scope
     return a.x<b.x;
            ^
0_0_37311479_23895.cpp:26:16: error: 'b' was not declared in this scope
     return a.x<b.x;
                ^