mutable 修改const修饰过的变量

#include <iostream>#include <iomanip>using namespace std;class C{  public:  C(int i):m_Count(i){}  int incr() const  {   return ++m_Count;  }  int decr() const  {    return --m_Count;  }    private:    mutable int m_Count;};int main(){C c1(5),c2(10);for(int tmp,i=0;i<10;i++){tmp = c1.incr();cout<<setw(tmp)<<setfill(' ')<<tmp<<endl;tmp = c2.decr();cout<<setw(tmp)<<setfill(' ')<<tmp<<endl;}return 0;}