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