View Compilation Error

0_0_22381314_25897.cpp:43:31: error: expected ';' at end of member declaration
  bool operator<(const nodes a)const   //set?lt;要重? {
                               ^
0_0_22381314_25897.cpp:46:3: error: expected unqualified-id before 'return'
   return y1>y2 || equal(y1,y2) && mark>a.mark;
   ^
0_0_22381314_25897.cpp:47:2: error: expected ';' after struct definition
  }
  ^
0_0_22381314_25897.cpp:45:19: error: 'a' was not declared in this scope
   double y2=cacul(a.id,a.mark);
                   ^
0_0_22381314_25897.cpp:45:24: error: 'a' was not declared in this scope
   double y2=cacul(a.id,a.mark);
                        ^
0_0_22381314_25897.cpp:48:1: error: expected declaration before '}' token
 };
 ^