?? 4_10.cpp
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#include <iostream>
using namespace std;
int gcd(int m, int n) //返回m 和n最大公約數
{ if (m<n) swap(m,n);
while (n>0) { int r=m%n; m = n; n = r; }
return m;
}
class Ratio
{ public:
Ratio(int n=0, int d=1) : num(n), den(d)
{ cout << "Common constructor called\n"; reduce(); }
Ratio(const Ratio& r):num(r.num), den(r.den) //拷貝構造函數
{ cout << "Copy constructor called\n"; }
void disp()
{cout <<num<<"/"<<den<<endl; }
private:
int num, den;
void reduce()
{ if (num == 0 || den == 0) {num = 0; den = 1; return; }
if (den < 0) {den *= -1; num *= -1; }
if (den == 1) return;
int sgn = (num<0?-1:1); int g = gcd(sgn*num,den);
num /= g; den /= g;
}
};
Ratio func(Ratio r) //初始化形參時調用拷貝構造函數
{Ratio s = r; return s; } //返回時調用拷貝構造函數
int main()
{ Ratio x(20,7);
cout<<"Ratio x is:"; x.disp();
Ratio y(x); //調用拷貝構造函數,用x初始化y
cout<<"Ratio y is:"; y.disp();
cout<<"Func() Start:"<<endl;
func(y); //調用拷貝構造函數3次
cout<<"Func() End"<<endl;
return 0;
}
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