#1.cpp

c++编程的几个小例子

#include <stdio.h>
#include <string.h>

class String {
        char *str;
        static int count;
  public:
        String() { count++; str = new char; *str = 0; }
        String( char * );
        ~String() { delete str; }
        operator char *();
        int operator < (String s) { return strcmp(str, s.str) < 0; }
        void print() { printf("%s", str); }

        friend int operator < (String, String);
        friend void report() ;
};

String::String(char *s)
{
        count++;
        str = new char[strlen(s) + 1];
        strcpy(str, s);
}

String::operator char*() {
        char *p = new char[strlen(str) + 1];
        strcpy (p, str);
        return p;        //use only a copy of str for protection
}

int operator < (String s1, String s2)
{
       return strcmp (s1.str, s2.str);
}

void report() 
{
       printf("Report on String usage: " );
       printf(" %d Strings created\n", String::count);
}

main()
{
        String s0 ;
        String s1 ("s1 == \"Hello C\"\n");
        String s2 ("s2 == \"Hello C++\"\n");
        String *sp = new String( "Hello world!" );
        
        char *cp = (char *) *sp;        //same as *cp = *sp 

        if ( !strcmp(cp, (char *) *sp) )
               printf("char *cp == (char *) *sp == \"%s\"\n", cp);

        s1.print();
        s2.print();

        if(s1.operator < (s2))
               printf("s1.operator < (s2)\n");
        if(operator < (s1, s2))
               printf("operator < (s1, s2)\n");
        report();
}
/* output:

char *cp == (char *) *sp == "Hello world!"
s1 == "Hello C"
s2 == "Hello C++"
s1.operator < (s2)
operator < (s1, s2)
Report on String usage:  4 Strings created

*/