1 #include <iostream>
 2 using namespace std;
 3 
 4 void fun(int a, int b, int c = 100);
 5 
 6 void fun(int a, int b, int c) // 这种情况不可以写，因为函数声明已写
 7 {
 8     cout << "a :: " << a << endl;
 9     cout << "b :: " << b << endl;
10     cout << "c :: " << c << endl;
11 }
12 
13 class A
14 {
15 public:
16     void fun1(int a, int b);
17     void fun2(int b, int c = 100);
18 };
19 
20 void A::fun1(int a, int b = 100)  // 这种情况可以写
21 {
22 }
23 
24 void A::fun2(int b, int c)  // 这种情况下不可以写，因为函数声明已写
25 {
26 }
27 
28 void main()
29 {
30     int n = 10;
31     fun(n * n, n, n++);
32 
33     system("pause");
34 }
35 
36 // run out:
37 /*
38 a :: 121
39 b :: 11
40 c :: 10
41 请按任意键继续. . .
42 */

 1 #include <iostream>
 2 using namespace std;
 3 
 4 class TestA
 5 {
 6 public:
 7     TestA(int a = 10, int b = 20, int c = 30, int d = 40)
 8         : m_nA(a)
 9         , m_nB(b)
10         , m_nC(c)
11         , m_nD(d)
12     {}
13 
14     int getA() { cout << "TestA::getA() [" << m_nA << "]" << endl;  return m_nA; }
15     int getB() { cout << "TestA::getB() [" << m_nB << "]" << endl;  return m_nB; }
16     int getC() { cout << "TestA::getC() [" << m_nC << "]" << endl;  return m_nC; }
17     int getD() { cout << "TestA::getD() [" << m_nD << "]" << endl;  return m_nD; }
18 
19 private:
20     int m_nA;
21     int m_nB;
22     int m_nC;
23     int m_nD;
24 };
25 
26 int sumFunc(int a, int b, int c, int d)
27 {
28     return (a + b + c + d);
29 }
30 
31 void main()
32 {
33     TestA aObj;
34     cout << "调用顺序及求和结果如下：" << endl;
35     cout << sumFunc(aObj.getA(), aObj.getB(), aObj.getC(), aObj.getD()) << endl;
36     system("pause");
37 }
38 
39 // run out:
40 /*
41 调用顺序及求和结果如下：
42 TestA::getD()[40]
43 TestA::getC()[30]
44 TestA::getB()[20]
45 TestA::getA()[10]
46 100
47 请按任意键继续. . .
48 */