main.cpp

#include <iostream>
using namespace std;

#include "MyString.h"

int main()
{
  MyString	a("hello"),		// Initializes using cString
				b = " world";	// Assigns value using assignment operator

	cout << "a (f): ";
	a.put();		// prints a
	cout << endl << "a (r): ";
	a.reverse();	// prints a in reverse
	cout << endl;

	MyString c;		
	c = a + b;			// concatenation of two MyStrings
	cout << "c:     " << c << endl;	// printing of c using insertion operator

	MyString d;
	d = a + " there";	// concatenation of MyString and a cString
	cout << "d:     " << d << endl;

	MyString e;	
	e = c.substr(3);	// Creation of substring using only position
	cout << "e:     " << e << endl;

	MyString f;
	f = c.substr(3, 5);	// Creation of substring using position and length
	cout << "f:     " << f << endl;

	MyString g(a);		// Initialization via copy constructor
	cout << "g:     " << g << endl;
	MyString h = b;		// Assigns value using assignment operator
	cout << "h:    " << h << endl;
	cout << "g + h: " << g + h << endl;
	
	MyString i;
	cout << "Enter a string: ";
	cin >> i;
	cout << "i:     " << i << endl;

	/* Error checking, ensuring that substr will work
	MyString i = a.substr(7);
	MyString j = a.substr(5, 9);
	*/

	return 0;
}

MyString.cpp

#include <iostream>
#include <cassert>
using namespace std;

#include "MyString.h"

MyString::MyString()
{
  length = 0;
	pData = new char[length + 1];
	pData[length] = '\0';
}

MyString::MyString(const char* cString)
{
	length = 0;
	do 
	{
		length++;
	} while (cString[length] != '\0');
	pData = new char[length + 1];
	for (int i = 0; i < length; i++)
	{
		pData[i] = cString[i];
	}
	pData[length] = '\0';
}

MyString::~MyString()
{
	delete [] pData;
	*pData = NULL;
	length = 0;
}

MyString::MyString(const MyString& s)
{
	copy(s);
}

MyString MyString::operator=(const MyString& s)
{
	copy(s);
	return *this;
}

MyString MyString::operator=(const char* cString)
{
	MyString temp(cString);
	return temp;
}

void MyString::copy(const MyString& s)
{
	length = s.length;
	pData = new char[length + 1];
	for (int i = 0; i < length; i++)
	{
		pData[i] = s.pData[i];
	}
	pData[length] = '\0';
}

void MyString::put()
{
	for (int i = 0; i < length; i++)
	{
		cout << pData[i];
	}
}

void MyString::reverse()
{
	for (int i = length-1; i >= 0; i--)
	{
		cout << pData[i];
	}
}

MyString MyString::operator+(const MyString& s)
{
	MyString cat;
	cat.length = length + s.length;
	cat.pData = new char[cat.length + 1];
	for (int i = 0; i < length; i++)
	{
		cat.pData[i] = pData[i];
	}
	for (int i = 0; i < s.length; i++)
	{
		cat.pData[length + i] = s.pData[i];
	}
	cat.pData[cat.length] = '\0';
	return cat;
}

MyString MyString::operator+(const char* cString)
{
	MyString temp(cString);
	MyString cat;
	cat = operator+(temp);
	return cat;
}

MyString MyString::substr(const int pos)
{
	assert (pos < length);

	MyString temp;
	temp.length = length - pos;
	temp.pData = new char[temp.length + 1];
	for (int i = 0; i < temp.length; i++)
	{
		temp.pData[i] = pData[pos + i];
	}
	temp.pData[temp.length] = '\0';
	return temp;
}

MyString MyString::substr(const int pos, const int len)
{
	assert(pos < length);
	assert(pos + len <= length);

	MyString temp;
	temp.length = len;
	temp.pData = new char[temp.length + 1];
	for (int i = 0; i < temp.length; i++)
	{
		temp.pData[i] = pData[pos + i];
	}
	temp.pData[temp.length] = '\0';
	return temp;
}

ostream& operator<<(ostream& os, const MyString& s)
{
	for (int i = 0; i < s.length; i++)
	{
		os << s.pData[i];
	}
	return os;
}

MyString.h

#ifndef __MYSTRING_H__
#define __MYSTRING_H__

class MyString
{
private:
  char*	pData;	
	int		length;	

public:
	MyString();
	MyString(const char* cString);
	~MyString();
	MyString(const MyString& s);
	MyString operator=(const MyString& s);
	MyString operator=(const char* cString);
	void put();
	void reverse();
	MyString operator+(const MyString& s);
	MyString operator+(const char* cString);
	MyString substr(const int pos);
	MyString substr(const int pos, const int len);

	friend ostream& operator<<(ostream& os, const MyString& s);
	friend istream& operator>>(istream& is, MyString& s);

private:
	void copy(const MyString& s);
};

#endif