1 @class A; 2 3 @class A; 4 5 @class A; 6 7 @class B; 8 9 @protocol P1; 10 11 @protocol P2; 12 @protocol P2; 13 14 struct S1; 15 struct S2; 16 struct S2; 17 18 #ifdef __cplusplus 19 template<typename T> class Vector; 20 #endif 21