C++primer 8.3.2節練習

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練習8.13

 1 #include <iostream> 2 #include <fstream> 3 #include <sstream> 4 #include <vector> 5  6 using namespace std; 7  8 struct PersonInfo 9 {10     string name;11     vector<string> phones;12 };13 14 string format(string)15 {16     return "format";17 }18 19 bool valid(string s)20 {21     if (s != "")22         return true;23     else24         return false;25 }26 27 int main()28 {29     ifstream in_file("people.txt");30     if (!in_file)31     {32         cerr << "no file?!" << endl;33         return 1;34     }35     string line, word;36     vector<PersonInfo> people;37     while (getline(in_file, line))38     {39         PersonInfo info;40         istringstream record(line);41         record >> info.name;42         while (record >> word)43             info.phones.push_back(word);44         people.push_back(info);45     }46 47     for (const auto &entry : people)48     {49         ostringstream formatted, badNums;50         for (const auto &nums : entry.phones)51         {52             if (!valid(nums))53             {54                 badNums << " " << nums;55             }56             else57                 formatted << " " << format(nums);58         }59         if (badNums.str().empty())60             cout << entry.name << " " << formatted.str() << endl;61         else62             cerr << "input error: " << entry.name << " invalid number(s) " << badNums.str() << endl;63     }64     system("pause");65     return 0;66 }

練習8.14

一個是避免拷貝，造成效率不高，第二是防止值被修改

C++primer 8.3.2節練習