重新实践c++primer上面的代码

又重新敲了敲c++primer上面的代码，觉得很有意思，讲的很细，c++真牛逼啊

 #include <iostream>
 #include <string>
 #include <cctype>
 #include <vector>
 #include <cassert>
 using namespace std;
 using std::ostringstream;

 int Add()
 {
     cout << "enter two numbers" << endl;

     int v1 = , v2 = ;
     cin >> v1 >> v2;
     cout << "the sum of" << v1 << "and" << v2
         << "is" << v1 + v2 << endl;
     return ;
 }

 int Unsigned()
 {
     unsigned u = , u2 = ;
     cout << u2 - u << endl;
     cout << u - u2 << endl;

     int i = , i1 = ;
     cout << i - i1 << endl;
     cout << i1 - i << endl;

     u = ;
     i = ;
     cout << i - u << endl;
     cout << u - i << endl;

     u = ;
     i = -;
     cout << i + i << endl;
     cout << u + i << endl;

 //     u = 10;
 //     cout << "hehe" << endl;
 //     while (u >= 0)
 //     {
 //         cout << u << endl;
 //         u--;
 //     }
     return ;
 }

 int reused = ;

 int Scope_Levels()
 {
     int unique = ;

     cout << reused << "" << unique << endl;
     int reused = ;
     cout << reused << "" << unique << endl;
     cout << ::reused << "" << unique << endl;
     return ;
 }

 int ReferenceTest()
 {
     int i = , &ri = i;

     cout << i << " " << ri << endl;
     i = ;
     cout << i << " " << ri << endl;

     ri = ;
     cout << i << "  " << ri << endl;

     return ;
 }

 int CompoundRef()
 {
     int i = , *p = &i, &r = i;
     cout << i << " " << *p << " " << r << endl;

     int j = , *p2 = &j;
     int *&pref = p2;
     cout << *pref << endl;

     pref = &i;
     cout << *pref << endl;

     *pref = ;
     cout << i << " " << *pref << " " << *p2 << endl;

     return ;
 }

 // int Convs()
 // {
 //     int i = 42;
 //     cout << i << endl;
 //
 //     if (i)
 //         i = 0;
 //     cout << i << endl;
 //
 //     bool b = 42;
 //     cout << b << endl;
 //
 //     int j = b;
 //     cout << j << endl;
 //
 //     double pi = 3.14;
 //     cout << pi << endl;
 //
 //     j = pi;
 //     cout << j << endl;
 //
 //     unsigned char c = -1;
 //     i = c;
 //     cout << i << endl;
 //
 //     return 0;
 // }

 int TestDoublePtr()
 {
     int ival = ;
     int* pi = &ival;
     int** ppi = &pi;

     cout << ival << "   " << *pi << "    " << **ppi << endl;

     int i = ;
     int* p1 = &i;

     *p1 = *p1 * *p1;
     cout << "i = " << i << endl;

     *p1 *= *p1;
     cout << "i = " << i << endl;
     return ;
 }

 int TestDecltype()
 {
     int a = ;
     decltype(a) c = a;
     decltype((a)) d = a;

     c++;
     cout << "a" << a << "c" << c << "d" << d << endl;

     d++;
     cout << "a" << a << "c" << c << "d" << d << endl;

     int A = , B = ;
     decltype((A)) C = A;
     decltype(A = B) D = A;

     C++;
     cout << A << C << D << endl;
     D++;
     cout << A << C << D << endl;

     return ;
 }

 int TestCctype()
 {
     string s("Hello World!!!");
     //     for (auto c : s)
     //         cout << c << endl;

     string::size_type punct_cnt = ;
     for (string::size_type c = ; c != s.size(); c++)
         if (ispunct(s[c]))
             ++punct_cnt;
     cout << punct_cnt << "        " << s << endl;

     string orig = s;
     for (string::size_type c = ; c != s.size(); c++)
         s[c] = toupper(s[c]);
     cout << s << endl;

     s = orig;
     string::size_type index = ;
     while (index != s.size() && !isspace(s[index]))
     {
         s[index] = toupper(s[index]);
         index++;
     }
     cout << s << endl;

     return ;
 }

 int TestArrayScores()
 {
     vector<unsigned> grades;
     const size_t sz = ;
     unsigned scores[sz] = {};
     unsigned grade;

     while(cin >> grade)
     {
         if (grade <= )
             scores[grade / ]++;
         grades.push_back(grade);
     }
     cout << "grades.size = " << grades.size() << endl;

     for (vector<unsigned>::const_iterator g = grades.begin(); g != grades.end(); g++)
         cout << *g << " ";
     cout << endl;

     for (size_t i = ; i != sz; i++)
         cout << scores[i] << " ";
     cout << endl;
     return ;

 }

 int TestGetline()
 {
     string line;
     while (getline(cin, line))
         cout << line << endl;
     return ;
 }

 int TestCstring()
 {
     string s1 = "A string example";
     string s2 = "A different string";

     if (s1 < s2)
         cout << s1 << endl;
     else
         cout << s2 << endl;

     const char ca1[] = "A string example";
     const char ca2[] = "A string example";

     if (strcmp(ca1, ca2) < )
         cout << ca1 << endl;
     else
         cout << ca2 << endl;

     const char *cp1 = ca1, *cp2 = ca2;
     cout << strcmp(cp1, cp2) << endl;
     cout << strcmp(cp2, cp1) << endl;
     cout << strcmp(cp1, cp1) << endl;

     cout << strlen(cp1) << endl;

     const unsigned sz =  +  + ;
     //char largeStr[sz];
     //pass
     return ;
 }

 int TestIterator()
 {
     string str("some string"), orig = str;
     if (!str.empty())
         cout << str[] << endl;
     if (!str.empty())
         str[] = toupper(str[]);
     cout << str << endl;

     str = orig;

     if (str.begin() != str.end())
     {
         string::iterator it = str.begin();
         *it = toupper(*it);
     }
     cout << str << endl;

     str = orig;
     for (string::size_type index = ; index != str.size() && !isspace(str[index]); index++)
         str[index] = toupper(str[index]);
     cout << str << endl;

     str = orig;
     for (string::iterator it = str.begin(); it != str.end() && !isspace(*it); it++)
         *it = toupper(*it);
     cout << str << endl;

     str = orig;
     string::size_type index = ;
     while (index != str.size() && !isspace(str[index]))
     {
         str[index] = toupper(str[index]);
         index++;
     }
     cout << str << endl;

     string::iterator beg = str.begin();
     while (beg != str.end() && !isspace(*beg))
     {
         *beg = toupper(*beg);
         beg++;
     }
     cout << str << endl;

     str = orig;
     for (string::const_iterator c = str.begin(); c != str.end(); c++)
         cout << *c;
     cout << endl;
     for (string::iterator c = str.begin(); c != str.end(); c++)
         *c = '*';
     cout << str << endl;

     str = orig;
     for (string::size_type ix = ; ix != str.size(); ix++)
         cout << str[ix];
     for (string::size_type ix = ; ix != str.size(); ++ix)
         str[ix] = '*';
     cout << str << endl;

     return ;

 }

 int arr[];
 int *p1[];
 int(*p2)[] = &arr;

 typedef int arrT[];

 arrT* func(int i);
 int(*func(int i))[];

 int odd[] = { , , , ,  };
 int even[] = { , , , ,  };

 int* elemPtr(int i)
 {
     return (i % ) ? odd : even;
 }

 int(*arrPtr(int i))[]
 {
     return (i % ) ? &odd : &even;
 }

 int (&arrRef(int i))[]
 {
     return (i % ) ? odd : even;
 }

 int TestBefore1()
 {
     int* p = elemPtr();
     int(*arrP)[] = arrPtr();
     int(&arrR)[] = arrRef();

     for (size_t i = ; i < ; i++)
         cout << p[i];
     cout << endl;
     for (size_t i = ; i < ; i++)
         cout << (*arrP)[i];
     cout << endl;
     for (size_t i = ; i < ; i++)
         cout << arrR[i];
     return ;
 }

 // struct ErrCode
 // {
 //     ErrCode(int i) : num(i) {}
 //     string msg()
 //     {
 //         ostringstream s;
 //         s << "ErrCode" << num;
 //         return s.str();
 //     }
 //     int num;
 // };

 string::size_type sumLength(const string&, const string&);
 string::size_type latgerLength(const string&, const string&);

 string::size_type sumLength(const string& s1, const string& s2)
 {
     return s1.size() + s2.size();
 }

 string::size_type largerLength(const string& s1, const string& s2)
 {
     return (s1.size() > s2.size()) ? s1.size() : s2.size();
 }

 string::size_type(*getFcn(const string& fetch))(const string&, const string&)
 {
     if (fetch == "sum")
         return sumLength;
     return largerLength;
 }

 int TestBefore2()
 {
     cout << getFcn("sum")("hello", "world") << endl;
     cout << getFcn("larger")("hello", "world") << endl;
     return ;
 }

 inline const string&
 shorterString(const string& s1, const string& s2)
 {
     return s1.size() <= s2.size() ? s1 : s2;
 }

 int TestBefore3()
 {
     string s1("successes"), s2("failure");
     cout << shorterString(s1, s2) << endl;
     cout << shorterString(s1, s2).size() << endl;
     cout << (s1.size() < s2.size() ? s1 : s2) << endl;
     return ;
 }

 void print(const int ia[], size_t size)
 {
 #ifndef NDEBUG
     cerr << "print(int *, size_t)" << "  " << size << endl;
 #endif
 }

 int TestErrorDeal()
 {
     string word = "foo";
     const string::size_type threshold = ;
     if (word.size() < threshold)
         cerr << "Error: " << __FILE__
         << " : in function " << TestErrorDeal
         << " at line " << __LINE__ << endl
         << "       Compiled on " << __DATE__
         << " at " << __TIME__ << endl
         << "       Word read was \"" << word
         << "\":  Length too short" << endl;
     word = "something longer than five chars";
     assert(word.size() > threshold);

     return ;
 }

这些东西一定是敲过一遍才觉得有趣，当然上边的东西也很初级，这基本上是前四章内重要的函数了，把它们弄在了一起，暂时先不整理了