View Compilation Error

0_0_13180569_28751.c: In function 'compare_point_by_y':
0_0_13180569_28751.c:31:12: error: 'temp' undeclared (first use in this function)
     return temp = ((Point*)a)->y - ((Point*)b)->y;
            ^
0_0_13180569_28751.c:31:12: note: each undeclared identifier is reported only once for each function it appears in