Question

C++ programming

You are to implement a MyString class which is our own limited implementation of the std:: string

Header file and test (main) file are given in below, code for mystring.cpp.

Here is header file

mystring.h

/* MyString class */

#ifndef MyString_H

#define MyString_H

#include <iostream>

using namespace std;

class MyString {

private:

   char* str;

   int len;

public:

   MyString();

   MyString(const char* s);

   MyString(MyString& s);

   ~MyString();

   friend ostream& operator <<(ostream& os, MyString& s); // Prints string

   MyString& operator=(MyString& s); //Copy assignment

   MyString& operator+(MyString& s); // Creates a new string by concantenating input string

};

#endif

Here is main file, the test file

testMyString.cpp

/* Test for MyString class */

#include <iostream>

#include "mystring.h"

using namespace std;

int main()

{

char greeting[] = "Hello World!";

MyString str1(greeting); // Tests constructor

cout << str1 << endl; // Tests << operator. Should print Hello World!

char bye[] = "Goodbye World!";

MyString str2(bye);

cout << str2 << endl; // Should print Goodbye World!

MyString str3{str2}; // Tests copy constructor

cout << str3 << endl; // Should print Hello World!

str3 = str1; // Tests copy assignment operator

cout << str3 << endl; // Should print Goodbye World!

str3 = str1 + str2; // Tests + operator

cout << str3 << endl; // Should print Hello World!Goodbye World!

return 0;

}

Answer 1

/* MyString class */
//mystring.h
#ifndef MyString_H

#define MyString_H

#include <iostream>

using namespace std;

class MyString {

private:

char* str;

int len;

public:

MyString();

MyString(const char* s);

MyString(MyString& s);

~MyString();

friend ostream& operator <<(ostream& os, MyString& s); // Prints string

MyString& operator=(MyString& s); //Copy assignment

MyString& operator+(MyString& s); // Creates a new string by concantenating input string

};

#endif

//testMyString.cpp
/* Test for MyString class */

#include <iostream>
#include<stdlib.h>
#include "mystring.h"

using namespace std;

ostream& operator <<(ostream& os, MyString& s)
{
   //print string and length of a string
   os << "String: "<<s.str<<endl;
   os<<"Length: "<<s.len<<endl;
   return os;
}
MyString ::MyString ()
{
   //allocate memory for the string
   str = (char *)malloc(sizeof(char) * 100);
   len = 0;
}
MyString:: MyString(const char *s)
{
   //copy contents of char *s to the str
   int length = string(s).length();;
   str = (char *)malloc(sizeof(char) * length);
   int pos = 0;
   while(s[pos]!='\0')
   {
       str[pos] = s[pos];
       pos++;
   }
   str[pos] = '\0';
   len = length;
}
MyString:: MyString (MyString &s)
{
   //copy contents of s.str to the str
   len = s.len;
   str = (char *)malloc(sizeof(char) * len);
   int pos = 0;
   while(s.str[pos]!='\0')
   {
       str[pos] = s.str[pos];
       pos++;
   }
   str[pos] = '\0';
}
MyString& MyString:: operator=(MyString& s)
{
   //copy contents of s.str and s.len to the str and len respectively
   len = s.len;
   str = (char *)malloc(sizeof(char) * len);
   int pos = 0;
   while(s.str[pos]!='\0')
   {
       str[pos] = s.str[pos];
       pos++;
   }
   str[pos] = '\0';
   return *this;
}
MyString& MyString:: operator+(MyString& s)
{
   //add string
   int pos = 0;
  
   while(s.str[pos]!='\0')
   {
       str[pos + len] = s.str[pos];
       pos++;
   }
   str[pos +len] = '\0';
   len += s.len;
   return *this;
  
}
MyString:: ~MyString()
{
   cout<<this<<" Object Destroyed"<<endl;
}
int main()
{

   char greeting[] = "Hello World!";

   MyString str1(greeting); // Tests constructor

   cout << str1 << endl; // Tests << operator. Should print Hello World!

   char bye[] = "Goodbye World!";

   MyString str2(bye);

   cout << str2 << endl; // Should print Goodbye World!

   MyString str3(str2); // Tests copy constructor

   cout << str3 << endl; // Should print Hello World!

   str3 = str1; // Tests copy assignment operator

   cout << str3 << endl; // Should print Goodbye World!

  
   str3 = str1 + str2; // Tests + operator

   cout << str3 << endl; // Should print Hello World!Goodbye World!
  
   return 0;

}