标准库中的重载/字符串类

Posted 2021-09-08 阿弥陀佛.a

有趣的重载：

#include <stdio.h>

const char endl = '\\n';

class Console
{
public:
    Console& operator << (int i)
    {
        printf("%d", i);
        
        return *this;
    }
    Console& operator << (char c)
    {
        printf("%c", c);
        
        return *this;
    }
    Console& operator << (const char* s)
    {
        printf("%s", s);
        
        return *this;
    }
    Console& operator << (double d)
    {
        printf("%f", d);
        
        return *this;
    }
};

Console cout;

int main()
{
    cout << 1 << endl;//想要连续传送，就必须写么写：
    cout << "D.T.Software" << endl;//Console& operator << (int i)
    //不能是void operator << (int i)
    
    double a = 0.1;
    double b = 0.2;
    
    cout << a + b << endl;
    
    return 0;
}

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>

using namespace std;


int main()
{
    printf("Hello world!\\n");
    
    char* p = (char*)malloc(16);
    
    strcpy(p, "D.T.Software");
    
    double a = 3;
    double b = 4;
    double c = sqrt(a * a + b * b);
    
    printf("c = %f\\n", c);
    
    free(p);
    
    return 0;
}

小结1

C语言中没有真正意义上的字符串，只有字符数组

#include <iostream>
#include <string>

using namespace std;

void string_sort(string a[], int len)
{
    for(int i=0; i<len; i++)
    {
        for(int j=i; j<len; j++)
        {
            if( a[i] > a[j] )
            {
                swap(a[i], a[j]);
            }
        }
    }
}

string string_add(string a[], int len)
{
    string ret = "";
    
    for(int i=0; i<len; i++)
    {
        ret += a[i] + "; ";
    }
    
    return ret;
}

int main()
{
    string sa[7] = 
    {
        "Hello World",
        "D.T.Software",
        "C#",
        "Java",
        "C++",
        "Python",
        "TypeScript"
    };
    
    string_sort(sa, 7);
    
    for(int i=0; i<7; i++)
    {
        cout << sa[i] << endl;
    }
    
    cout << endl;
    
    cout << string_add(sa, 7) << endl;
    
    return 0;
}

#include <iostream>
#include <sstream>
#include <string>

using namespace std;


#define TO_NUMBER(s, n) (istringstream(s) >> n)
#define TO_STRING(n) (((ostringstream&)(ostringstream() << n)).str())

int main()
{

    double n = 0;
   
    if( TO_NUMBER("234.567", n) )
    {
        cout << n << endl;    
    }

    string s = TO_STRING(12345);

    cout << s << endl;     
    
    return 0;
}

#include <iostream>
#include <string>

using namespace std;

string operator >> (const string& s, unsigned int n)
{
    string ret = "";
    unsigned int pos = 0;
    
    n = n % s.length();
    pos = s.length() - n;
    ret = s.substr(pos);
    ret += s.substr(0, pos);
    
    return ret;
}

int main()
{
    string s = "abcdefg";
    string r = (s >> 3);
    
    cout << r << endl;
    
    return 0;
}

右移一位思路：

小结