【C++ Primer】 第六章 函数基础

函数基础

练习

练习6.6

 1 #include<iostream>
 2 using namespace std;
 3
 4 double myADD(double num1, double num2)
 5 {
 6     double result = num1 + num2;
 7     static unsigned iCnt = 0;
 8     ++iCnt;
 9     cout << "该函数累计执行了" << iCnt << "次" << endl;
10     return result;
11 }
12
13 int main()
14 {
15     double num1, num2;
16     cout << "请输入两个数：";
17     while (cin >> num1 >> num2)
18     {
19         cout << num1 << "与" << num2 << "的求和结果："
20             << myADD(num1, num2) << endl;
21     }
22     return 0;
23 }

运行结果：

练习6.7

 1 #include<iostream>
 2 using namespace std;
 3
 4 unsigned myCnt()
 5 {
 6     static unsigned iCnt = -1;
 7     ++iCnt;
 8     return iCnt;
 9 }
10 int main()
11 {
12     cout << "请输入任意字符按回车键任意键" << endl;
13     char ch;
14     while (cin >> ch)
15     {
16         cout << "函数myCnt的执行次数：" << myCnt() << endl;
17     }
18     return 0;
19 }

参数传递

•使用引用避免拷贝

bool isShorter(const string &s1, const string &s2)
{
    return s1.siz2() < s2.size();
}

•使用引用形参返回额外信息

//返回s中c第一次出现的位置
//引用形参occurs负责统计c出现的次数
string::size_type find_char(const string &s, char c, string::size_type &occurs)
{
    auto ret = s.size();
    occurs = 0
    for(decltype(ret) i = 0; i != size(), ++i)
    {
        if(s[i] == c)
        {
            if(ret == s.size())
                ret = i;
            ++occurs;
        }
    }
    return ret;
}

auto = find_char(s, ‘o‘, ctr);

练习

练习6.11

 1 #include<iostream>
 2 using namespace std;
 3
 4 int reset(int &i)
 5 {
 6     i = 0;
 7     return i;
 8 }
 9
10 int main()
11 {
12     int num = 10;
13     cout << "重置前：num = " << num << endl;
14     reset(num);
15     cout << "重置后：num = " << num << endl;
16     return 0;
17 }

原文地址：https://www.cnblogs.com/sunbines/p/8715703.html