// Source: "Software Design ...", John A Robinson, Newnes, 2004, page 138.
#include <iostream>
#include <cstring>
using namespace std;
int error(char *p)
	{
	cerr << p << "\n";
	return 0;
	}

class String
	{
	char *buf;
	int  len;	// Length does not include terminating '\0'
public:
	// Constructors
	String (const char *p)		// String x("abc");
		{
		len = strlen(p);
		buf = new char[len + 1];
		strcpy(buf, p);
		}
	String () { buf = new char; buf[0] = 0; len = 0;}	// String x;
	// Note that String of length 0+1 created, so that delete buf
	// will work correctly when the destructor is called.
	// Destructor
	~String() { delete [] buf;}
	// Assignment to and from Strings
	String& operator=(const char *p);	// x = "abc";
	String& operator=(const String &str);	// y = x;
	char& operator[](int i);		// c = x[4]; x[5] = 'a';
	friend ostream& operator<<(ostream& out, const String &x);
	friend istream& operator>>(istream& in, String &x);
	// Tests
	friend int operator==(const String &x, const char *s)
		{
		return (strcmp(x.buf, s) == 0);
		}
	friend int operator==(const String &x, const String &y)
		{
		return (strcmp(x.buf, y.buf) == 0);
		}
	friend int operator!=(const String &x, const char *s)
		{
		return (strcmp(x.buf, s) != 0);
		}
	friend int operator!=(const String &x, const String &y)
		{
		return (strcmp(x.buf, y.buf) == 0);
		}
	friend int strlen(const String &x)
		{
		return x.len;
		}
	};

String& String::operator=(const char *p)
	{
	// Delete old String
	delete [] buf;
	len = strlen(p);
	buf = new char[len + 1];
	strcpy(buf, p);
	return *this;
	}

String& String::operator=(const String &str)
	{
	if (str.buf != buf)	// Protect against x = x;
		{
		delete [] buf;
		len = str.len;
		buf = new char[len + 1];
		strcpy(buf, str.buf);
		}
	return *this;
	}

char& String::operator[](int i)		
	{
	if (i < 0 || i >= len) {
		error("index out of range");
		i = 0;
		}
	return buf[i];
	}
ostream& operator<<(ostream& out, const String &x)
	{
	return out << x.buf;
	}
istream& operator>>(istream&in, String &x)
	{
	char tempbuf[256];
	// Set maximum number of chars to read
	in.width(256);
	// And get a whitespace-separated word
	in >> tempbuf;
	// Copy string over
	x = tempbuf;
	return in;
	}

main()
	{
	String st[100];
	int n;
	cout << "Enter several lines of text:\n";
	for (n = 0; n < 100; n++)
		{
		cin >> st[n];
		String test;
		cout << (test = st[n]) << '\n';
		for (int j=0; j < n; j++)	// Search for a match
			{
			if (st[j] == test)
				cout << "Seen before at line " << j << '\n';
			}
		if (test == "done")
			break;
		}
	cout << "Here are the input lines in reverse order, with modifications\n";
	for (int i=n-1; i >= 0; i--)
		{
		st[i][i] = 'X';
		cout << st[i] << '\n';
		}
	return 0;
	}