C++ primer 讀書筆記四

第六章 函數

• 傳入引用參數
  

吐槽：c++ primer 這本書感覺不行，關於很多概念講不清
同時代碼存在不具備連續以及調測性

#include "a.hpp"
#include<iostream>
#include<vector>
using std::string;
using std::cout;
using  std::endl;
using namespace std;
//using namespace string;


string::size_type findchar(const string &s ,char c,string::size_type &occurs)
{
    auto ret = s.size();
    occurs = 0;
    for (decltype(ret) i = 0;i <s.size(); i++) {
        if(s[i]==c)
        {
            if(ret == s.size())
            {
                ret =i;
                cout<<" ret ="<<ret<<endl;

            }
            ++occurs;
        }
    }


    return ret;
}

int main()
{
    string str("liu chuan wu");
    string::size_type count  ;
    string::size_type &sount = count;
    string::size_type ret=  findchar(str,'u', sount)  ;
    cout<<sount<<endl;
    cout<<ret<<endl;


}

findchar 函數必須傳入引用
ret =2
3
2
Program ended with exit code: 0

指針版本

#include<iostream>
#include<vector>
using std::string;
using std::cout;
using  std::endl;
using namespace std;
//using namespace string;


string::size_type findchar(const string s ,char c,string::size_type* occurs)
{
    auto ret = s.size();
    *occurs = 0;
    for (decltype(ret) i = 0;i <s.size(); i++) {
        if(s[i]==c)
        {
            if(ret == s.size())
            {
                ret =i;
                cout<<" ret ="<<ret<<endl;

            }
            ++(*occurs);
        }
    }


    return ret;
}

int main()
{
    string str("liu chuan wu");
    string::size_type count =0 ;
    //string::size_type *sount = &count;
    string::size_type ret=  findchar(str,'u', &count)  ;
    cout<<count<<endl;
    cout<<ret<<endl;


}

結果是相同的