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

6.1 - The ISO C++ Standard

6.1.1 - Implementations

6.1.2 - The Basic Source Character Set

6.2 - Types

6.2.1 - Fundamental Types

6.2.2 - Booleans

int* p;
...
if (p) {  // p!=nullptr
    ...
}

6.2.3 - Character Types

6.2.3.1 - Signed and Unsigned Characters

6.2.3.2 - Character Literals

6.2.4 - Integer Types

more integer types in <cstdint>

6.2.4.1 - Integer Literals

  • Decimal: 63
  • Octal: 063

  • Hexadecimal: 0x63

  • int: 3
  • unsigned int: 3U
  • long: 3L

6.2.4.2 - Types of Integer Literals

6.2.5 - Floating-Point Types

6.2.5.1 - Floating-Point Literals

  • 1.23
  • 1.23e-15
  • 3.1415F
  • 3.1415L
  • 2.9e-3L

6.2.6 - Prefixes and Suffixes

6.2.7 - void

void f();   // function f return nothing.
void* pv;   // pointer to object of unknown type.

6.2.8 - Sizes

    cout << "size of long: " << sizeof(1L) << endl;
    cout << "size of long long: " << sizeof(1LL) << endl;

    cout << "max float == " << numeric_limits<float>::max() << endl;
    cout << "char is signed == " << numeric_limits<char>::is_signed << endl;
    cout << "true: " << true << endl;

size of long: 8
size of long long: 8
max float == 3.40282e+38
char is signed == 1
true: 1

6.2.9 - Alignment

6.3 - Declarations

6.3.1 - The Structure of Declarations

6.3.2 - Declaring Multiple Names

6.3.3 - Names

suggestions for naming conventions.

6.3.3.1 - Keywords

6.3.4 - Scope

  • Local scope
  • Class scope
  • Namespace scope
  • Global scope
  • Statement scope
  • Function scope

6.3.5 - Initialization

X a1 {v};   // 建議使用這種
X a2 = {v};
X a3 = v;
X a4(v);

// trap!
auto z1 {99}   // z1 is an initializaer_list<int> !!!
auto z2 = 99   // z2 is an int

vector<int> v1 {99};  // 一個元素，值為99
vector<int> v2(99);   // 99個元素，皆為默認值0

// 最好是把默認值 {} 寫上,如:
int x {};             // 0
char buf[1024] {}     // buf[i] == 0
char* p {};           // nullptr
vector<int> v {};     // empty vector
string s {};          // ""
int* p {new int{10}}  // *p == 10
char* q { new char[1024]{} }   // q[i] == 0

6.3.5.1 - Missing Initializers

只有當使用很大的 buffer 時候，不刻意賦給初始值才有提升效能的好處。
一般狀況下，最好賦給初始值。

global, namespace, local static, static member 的變量會被自動賦予 {} 初始值。

local, heap objects 不會自動獲得初值。

6.3.5.2 - Initializer Lists

6.3.6 - Deducting a Type: auto and decltype()

6.3.6.1 - The auto Type Specifier

6.3.6.2 - auto and {}-list

當使用 auto 宣告時候，最好使用 =, 不要用 {}, 除非是要一個 list

auto i = 1;       //int
auto i = {1};     // list of int, one element
auto i = {1, 2};  // list of int, two elements

6.3.6.3 - The decltype() Specifier

templace<class T, class U>
auto operator+(const Matrix<T>& a, const Matrix<U>& b)  ->  Matrix<decltype( T{}+U{} )>;

6.4 - Objects and Values

lvalue is an expression that refers to an object.

constants are also lvalues.

6.4.1 - Lvalues and Rvalues

rvalue : a value that is not a lvalue.

  • (i) Has Identity : 有變量名，指標指向，因此可辨識兩個 object 是否是同一個。

  • (m) Movable : 相對 copy 來說。

  • lvalue : i, !m
  • rvalue : m
  • prvalue : pure rvalue : !i, m
  • glvalue : generalized lvalue : i
  • xvalue : eXtraordinary, eXpert only : i, m

每一個 statement 必須是 lvalue 或 rvalue 的任一個；不可以都是。

6.4.2 - Lifetimes of Objects

  • Automatic: 在 function scope 內，隨著 function 生滅的 stack 變數。
  • Static: global, namespace, static 變數，在整個 program 執行期間存在。
  • Free store: new / delete
  • Temporary objects: like automatic
  • Thread-local objects: 跟著 thread 生滅。

6.5 - Type Aliases

using Pchar = char*;
using PF = int(*)(double)  //pointer to function taking a double and returning an int.

// older syntax
typedef int int32_t;        // equivalent to :  using int32_t = int;
typedef void(*PtoF)(int);   // equivalent to :  using PtoF = void(*)(int);