函数指针
int add(int x,int y){return x+y;}
int minus(int x,int y){return x-y;}
main(){
int (*p)(int,int) = add;
(*p)(1,2);
int (*p[2])(int,int);
p[0]=add;
p[1]=minus;
(*p[0])(1,2);
(*p[1])(2,1);
}
int add(int x,int y){return x+y;}
int minus(int x,int y){return x-y;}
main(){
int (*p)(int,int) = add;
(*p)(1,2);
int (*p[2])(int,int);
p[0]=add;
p[1]=minus;
(*p[0])(1,2);
(*p[1])(2,1);
}