C + + Primer notes

• Chapter 2
  • Low-level & top-level const
  • constexpr
  • Type Alias
    • Pointer alias
  • Decltype
    • Decltype and references
• Chapter 3
  • • Type aliases for multidimensional arrays
• Chapter 6 function
  • Declaring a function that returns an array pointer
  • function overloading
    • Const_cast
  • function arguments
    • Default actual parameters
    • Default argument initial value
• Chapter Class 7
  • Characteristics
    • Variable data members
    • Returns the member function of the *this
    • Const-based overloading
  • Delegate constructors
• Chapter 8
  • String stream
    • Istringstream
    • Ostringstream
• Chapter 9
  • Container operations
    • Emplace
  • Adapter
• Chapter 10
  • Generic algorithms
  • Lambda expression

Chapter 2low-level & top-level const

int i = 0;int *const p1 = &i;         // top-levelconst int c1 = 42;          // top-levelconst int *p2 = &ci;        // low-levelconst int *const p3 = p2;   // low-level (left) & top-level (right)const int &r = ci;          // both low-level

constexpr

constexpr int mf = 20;

Type Alias

typedef double wages;       // classictypedef wages base, *p;using SI = Sales_item;      // C++11

Pointer alias

typedef char *pstring;const pstring cstr = 0;     // cstr是指向char的常量指针const pstring *ps;          // ps是一个指针，它的对象是指向char的常量指针const char *cstr = 0;       // [注意]与 const pstring cstr 不同！

Decltype

decltype(f()) sum = x;

Decltype and references

decltype(i) e;      // 正确decltype((i)) d;    // 错误, d 是 int&

Chapter 3 Type aliases for multi-dimensional arrays

using int_array = int[4];typedef int int_array[4];

Chapter 6 function declares a function that returns an array pointer

int (*func(int i))[10];auto func(int i) -> int(*)[10];    // lamabda

function Overloading Const_cast

const string &shorterString(const string&, const string &);// 使用const_cast重载原函数的非常量版本string &shorterString(string &s1, string &s2){    auto &r = shorterString(                const_cast<const string&>(s1),                const_cast<const string&>(s2));    return const_cast<string&>(r);}

function argument default argument

typedef string::size_type sz;string screen(sz, sz, char = ' ');string screen(sz, sz, char = '*');      // 错误string screen(sz = 24, sz = 80, char);  // 正确

Default argument initial value

sz wd = 80;char def = ' ';sz ht();string screen(sz = ht(), sz = wd, char = def);string window = screen(); // 调用 screen(ht(), 80, ' ');

Chapter 7 Class attribute variable data member

keyword mutable

Returns the member function of the *this

Returning *this means returning an object as an lvalue, meaning that a series of operations can be concatenated in an expression

myScreen.move(4, 0).set('#');

Const-based overloading

class Screen {public:    Screen &display(std::ostream &os) {        do_display(os); return *this;    }    const Screen &display(std::ostream &os) const {        do_display(os); return *this;    }}Screen myScreen(5, 3);const Screen blank(5, 3);myScreen.set('#').display(cout);    // 非常量版本blank.display(cout);                // 常量版本

Delegate constructors

A delegate constructor performs its own initialization process using the other constructors of the class it belongs to

Chapter 8string Stream Istringstream

istringstream record(line);record >> info.name;

Ostringstream

ostringstream formatted;formatted << anyString << endl;cout << formatted.str();

Chapter 9 Container Operation Emplace

The following equivalence

c.emplace_back(args);c.push_back(T(args));

Adapter

stack<int, vector<int>>stk; // 使用vector构造stack适配器

Chapter 10 Generic algorithm

• back_inserterInserting iterators
• for_each

Lambda expression

• Value capture
• Reference capture
• Implicit capture

C + + Primer notes