PPPUC++ Reading Note

1. CH. 17 Memory, Address
2. CH. 18 Vector and Array

1 CH. 17 Memory, Address

int main()
{
  char a = 'a';
  char b = 'b';
  void *pv = &a;
  int *pa = (int*)pv;
  std:: cout <<*pa<<std::endl;
  *pa = 65535;
  std:: cout <<(char*)&a<<" "<<(char*)&b<<std::endl;
  std:: cout <<a<<" "<<b<<std::endl;
  return 0;
}

�� b��
� b

实测堆上分配的内存并没有溢出

int* 和 char* 不能直接互相赋值的原因: 索引数组时地址跨越长度

1.1 初始化:

为了避免误用未初始化的变量, 尽量保证变量在被声明的同时初始化.

1.2 空指针:

c++11 引入了nullptr, 旨在于解决null的二义性问题

1.3 Free-Store:

Free-Store由Store Manager管理

1.4 析构函数:

占用Free-Store的类都需要析构函数

1.5 指针和引用:

传值和传指针: 指针允许nullptr, 可能需要额外写防御代码.

2 CH. 18 Vector and Array

initializer_list
copy constructor
copy assignment

2.1 Copying

2.2 Moving

&& ?

2.3 explicit

2.4 Get & Set

索引靠重载[]运算符实现, 并返回reference.

若返回值则只能get无法set(可用作const版本), 返回指针则书写起来比较别扭.

2.5 Array

array的问题: 编译器难以做到边界检查 pointer arithmetic

2.6 Excrise

#include <iostream> using namespace std;

class Vector { int sz; double * elem; public: Vector(int s): sz{s}, elem{new double[s]} { for(int i = 0; i < sz; i++) elem[i] = 0; }

Vector(initializer_list<double> lst): sz{(int)lst.size()},elem{new double[lst.size()]} { copy(lst.begin(),lst.end(),elem); }

Vector(const Vector&);

Vector& operator=(const Vector&);

~Vector(){delete[] elem;} void Set(int, double); void Print(); };

void Vector::Set(int index, double value) { if (index >= sz) return; elem[index] = value; }

void Vector::Print() { for (int i = 0; i < sz; i++) { cout<<(elem[i])<<endl; } }

Vector::Vector(const Vector& arg) :sz(arg.sz),elem(new double[arg.sz]) { copy(arg.elem,arg.elem+arg.sz,elem); }

Vector& Vector::operator=(const Vector& arg) { double *d = new double[arg.sz]; copy(arg.elem,arg.elem+arg.sz,d); delete[] elem; elem = d; sz = arg.sz; return *this; }

// exc 1 char strup(const char a) { int sz = 0; while ( a[sz] != 0 ) sz++;

char * res = new char[sz+1]; for(int i = 0; i <= sz; i++) res[i] = *a+i;

return res; }

// exc 2

int main(int argc, const char * argv[]) {

return 0; }

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