C++primer 14.3.1节练习
练习14.16
1 #include <iostream> 2 #include <string> 3 #include <utility> 4 #include <memory> 5 #include <algorithm> 6 7 using namespace std; 8 9 class String { 10 friend ostream &operator<<(ostream &os, String &s); 11 friend bool operator==(const String& lhs, const String& rhs); 12 friend bool operator!=(const String& lhs, const String& rhs); 13 public: 14 String() : element(nullptr), first_free(nullptr) {} 15 String(char *); 16 private: 17 static allocator<char> alloc; 18 char *element; 19 char *first_free; 20 }; 21 22 allocator<char> String::alloc; 23 bool operator==(const String& lhs, const String& rhs); 24 bool operator!=(const String& lhs, const String& rhs); 25 26 int main() 27 { 28 String s1; 29 String s2("ello"); 30 String s3("hello world"); 31 cout << s1; 32 cout << s2; 33 cout << s3; 34 cout << (s2 == s3); 35 cout << endl; 36 system("pause"); 37 return 0; 38 } 39 40 String::String(char *s) 41 { 42 int i = 0; 43 while (s[i] != '\0') 44 ++i; 45 auto newloc = alloc.allocate(i); 46 auto dest = newloc; 47 for (auto count = 0; count != i;++count) 48 alloc.construct(dest++, s[count]); 49 element = newloc; 50 first_free = dest; 51 } 52 53 ostream & operator<<(ostream &os, String &s) 54 { 55 while (s.element != s.first_free) 56 { 57 os << *(s.element); 58 s.element++; 59 } 60 cout << endl; 61 return os; 62 // TODO: 在此处插入 return 语句 63 } 64 65 ostream &operator<<(ostream &os, bool b); 66 67 bool operator==(const String & lhs, const String & rhs) 68 { 69 auto i = lhs.element; 70 auto j = rhs.element; 71 if ((lhs.first_free - lhs.element) != (rhs.first_free - rhs.element)) 72 return false; 73 while ((i != lhs.first_free) && (j != rhs.first_free)) 74 if (*(i++) != *(j++)) 75 return false; 76 } 77 78 bool operator!=(const String & lhs, const String & rhs) 79 { 80 return !(lhs == rhs); 81 }
这段代码不知道为何结果不对，实在找不出来错误在哪。
1 bool operator==(const StrVec & lhs, const StrVec & rhs) 2 { 3 auto i = lhs.elements; 4 auto j = rhs.elements; 5 if (lhs.size() == rhs.size()) 6 { 7 while (i != lhs.first_free) 8 { 9 if (*i == *j) 10 { 11 ++i; 12 ++j; 13 } 14 } 15 return true; 16 } 17 else 18 return false; 19 }
类似的代码放在StrVec类中是正确的。
练习14.17
略
