C++深度解析教程笔记5

第10课 - C++ 中的新成员

实验-new

#include <stdio.h>

int main()
{
    int* p = new int;
    
    *p = 5;
    *p = *p + 10;
    
    printf("p = %p\n", p);
    printf("*p = %d\n", *p);
    
    delete p;
    
    p = new int[10];
    
    for(int i=0; i<10; i++)
    {
        p[i] = i + 1;
        
        printf("p[%d] = %d\n", i, p[i]);
    }
    
    delete[] p;
    
    return 0;
}

/*
E:\test>g++ 10-1.cpp

E:\test>a
p = 0000000000EB6E90
*p = 15
p[0] = 1
p[1] = 2
p[2] = 3
p[3] = 4
p[4] = 5
p[5] = 6
p[6] = 7
p[7] = 8
p[8] = 9
p[9] = 10
*/

实验-new初始化

#include <stdio.h>

int main()
{
    int* pi = new int(1);
    // int* pa = new int[1];
    
    float* pf = new float(2.0f);
    char* pc = new char('c');

    printf("*pi = %d\n", *pi);
    printf("*pf = %f\n", *pf);
    printf("*pc = %c\n", *pc);
    
    delete pi;
    delete pf;
    delete pc;
    
    return 0;
}
/*
*pi = 1
*pf = 2.000000
*pc = c
*/

实验-命名空间

#include <stdio.h>

namespace First
{
    int i = 0;
}

namespace Second
{
    int i = 1;
    
    namespace Internal
    {
        struct P
        {
            int x;
            int y;
        };
    }
}

int main()
{
    using namespace First;
    using Second::Internal::P;
    
    printf("First::i = %d\n", i);
    printf("Second::i = %d\n", Second::i);
    
    P p = {2, 3};
    
    printf("p.x = %d\n", p.x);
    printf("p.y = %d\n", p.y);
    
    return 0;
}
E:\test>g++ 10-3.cpp

E:\test>a
First::i = 0
Second::i = 1
p.x = 2
p.y = 3

第11课 - 新型的类型转换

实验-C方式的强制类型转换

#include <stdio.h>

typedef void(PF)(int);

struct Point
{
    int x;
    int y;
};

int main()
{
    int v = 0x12345;
    PF* pf = (PF*)v;
    char c = char(v);
    Point* p = (Point*)v;
    
    pf(5);
    
    printf("p->x = %d\n", p->x);
    printf("p->y = %d\n", p->y);

    return 0;
}
//error

实验-新式强制类型转换

#include <stdio.h>

void static_cast_demo()
{
    int i = 0x12345;
    char c = 'c';
    int* pi = &i;
    char* pc = &c;
    
    c = static_cast<char>(i);
    //pc = static_cast<char*>(pi);//error: invalid static_cast from type 'int*' to type 'char*'
     
}

void const_cast_demo()
{
    const int& j = 1;
    int& k = const_cast<int&>(j);
    
    const int x = 2;
    int& y = const_cast<int&>(x);
    
    //int z = const_cast<int>(x);//error: invalid use of const_cast with type 'int', which is not a pointer, reference, nor a pointer-to-data-member type
    
    k = 5;
    
    printf("k = %d\n", k);
    printf("j = %d\n", j);
    
    y = 8;
    
    printf("x = %d\n", x);
    printf("y = %d\n", y);
    printf("&x = %p\n", &x);
    printf("&y = %p\n", &y);
}

void reinterpret_cast_demo()
{
    int i = 0;
    char c = 'c';
    int* pi = &i;
    char* pc = &c;
    
    pc = reinterpret_cast<char*>(pi);
    pi = reinterpret_cast<int*>(pc);
    pi = reinterpret_cast<int*>(i);
    //c = reinterpret_cast<char>(i); // error: invalid cast from type 'int' to type 'char'
}

void dynamic_cast_demo()
{
    int i = 0;
    int* pi = &i;
    //char* pc = dynamic_cast<char*>(pi);//error: cannot dynamic_cast 'pi' (of type 'int*') to type 'char*' (target is not pointer or reference to class)
}

int main()
{
    static_cast_demo();
    const_cast_demo();
    reinterpret_cast_demo();
    dynamic_cast_demo();
    
    return 0;
}

小结