在閱讀 The C++ Programming Language 4th Edition - Bjarne Stroustrup 過程中的紀錄。

7.1 - Introduction

Pointer : holding address
Reference : using address

7.2 - Pointers

int* pi;           // pointer to int
char** ppc;        // pointer to pointer to char
int* ap[15];       // array of 15 elements of pointer to int
int (*fp)(char*);  // pointer to function taking argument:char* , return int
int* f(char*);     // function taking argument:char*, return a pointer to int

7.2.1 - void*

Point to an object of unknown type.

Pointers to functions and pointers to members cannot be assigned to void*

7.2.2 - nullptr

7.3 - Arrays

array 的大小必須是 constant expression.
如果需要動態大小，用 vector.

int a1[10];                 // in static storage

void f() {
    int a2 [20];            // on stack
    int* p = new int[40];   // on the free store
}

7.3.1 - Array Initializers

7.3.2 - String Literal

sizeof("Bohr") == 5   // const char[5]

7.3.2.1 - Raw Character Strings

string s = R"(ccc)"

string s = R"***("  words("))  ")***"
//               "  words("))  "
// 也可以有斷行

7.3.2.2 - Larger Character Sets

L"abcd"     // type: const wchar_t[], terminated by L'\0'

7.4 - Pointers into Arrays

7.4.1 - Navigating Arrays

    int a_size = 5;
    int a[] = {11,22,33,44,55};
 
    for(int i=0; i!=a_size; ++i) cout << a[i] << ", ";
    cout << endl;

    cout << "      a[2]  == " << a[2] << endl;
    cout << "*(&a[0]+2)  == " << *(&a[0]+2) << endl;
    cout << "  *(j + a)  == " << *(2 + a) << endl;
    cout << "      2[a]  == " << 2[a] << endl;

    // C standard defines:
    // a[b] == *(a + b)

range-for works for array of known size, does not work for array of unknown size.

for(int x : a) use(x)
// okay for a[3]
// error inside: void funcp(int a[], int size)

array 是 low-level 的操作，最好避免；使用高階的 vector 就行。

7.4.2 - Multidimensional Arrays

int ma[3][5]

7.4.3 - Passing Arrays

7.5 - Pointer and const

const 對象不可被賦值 (assigned), 所以必須宣告時候就初始化 (initialized)

const char* pc;            // 1.a  指向 constant 的 pointer
char const* pc;            // 1.b  指向 constant 的 pointer, 同 1.a
char *const cp = s;        // 2    pointer 本身是 constant
const char *const cpc = s; // 合上兩者 1+2

7.6 - Pointers and Ownership

new 出來的 resource 必須被 delete

7.7 - References

7.7.1 - Lvalue References

7.7.2 - Rvalue References

Lvalue: 具有識別符，名稱，指標指向的對象。
Rvalue: 無識別符，無變量名稱，通常是僅存於 scope 內的臨時數值。

template<class T> 
class vector {
    vector(const vector& r);   // copy constructor
    vector(vector&& r);        // move constructor
};

vector<string> s;
vector<string> s2 {s};           // s is Lvalue, so use copy constructor
vector<string> s2 {s + "tail"};  // s+"tail" is Rvalue, so use move constructor

7.7.3 - References to References

7.7.4 - Pointers and References

Matrix operator+(const Matrix&, const Matrix&);       // valid
Matrix operator-(const Matrix*, const Matrix*);       // error: no user-defined type argument.