using System;

public class Document { // Type allowing the document to be viewed like an array of words: public class WordCollection { readonly Document document; // The containing document

internal WordCollection(Document d) { document = d; } // Helper function -- search character array "text", starting at // character "begin", for word number "wordCount." Returns false // if there are less than wordCount words. Sets "start" and // length" to the position and length of the word within text: private bool GetWord(char[] text, int begin, int wordCount, out int start, out int length) { int end = text.Length; int count = 0; int inWord = -1; start = length = 0;

for(int i=begin;i<=end;i++) { bool isLetter = i<end && Char.IsLetterOrDigit(text[i]);

if(inWord>=0) { if(!isLetter) { if(count++ == wordCount) { start = inWord; length = i - inWord; return true; } inWord = -1; } } else { if(isLetter) inWord = i; } } return false; }

// Indexer to get and set words of the containing document: public string this[int index] { get { int start, length; if(GetWord(document.TextArray, 0, index, out start, out length)) return new string(document.TextArray, start, length); else throw new IndexOutOfRangeException(); } set { int start, length; if(GetWord(document.TextArray, 0, index, out start, out length)) { // Replace the word at start/length with the // string "value": if(length == value.Length) { Array.Copy(value.ToCharArray(), 0, document.TextArray, start, length); } else { char[] newText = new char[document.TextArray.Length + value.Length - length]; Array.Copy(document.TextArray, 0, newText, 0, start); Array.Copy(value.ToCharArray(), 0, newText, start, value.Length); Array.Copy(document.TextArray, start + length, newText, start + value.Length, document.TextArray.Length - start - length); document.TextArray = newText; } } else throw new IndexOutOfRangeException(); } }

// Get the count of words in the containing document: public int Count { get { int count = 0, start = 0, length = 0; while (GetWord(document.TextArray, start + length, 0, out start, out length)) ++count; return count; } } }

// Type allowing the document to be viewed like an "array" // of characters: public class CharacterCollection { readonly Document document; // The containing document

internal CharacterCollection(Document d) { document = d; }

// Indexer to get and set characters in the containing document: public char this[int index] { get { return document.TextArray[index]; } set { document.TextArray[index] = value; } }

// Get the count of characters in the containing document: public int Count { get { return document.TextArray.Length; } } }

// Because the types of the fields have indexers, // these fields appear as "indexed properties": public readonly WordCollection Words; public readonly CharacterCollection Characters;

private char[] TextArray; // The text of the document.

public Document(string initialText) { TextArray = initialText.ToCharArray(); Words = new WordCollection(this); Characters = new CharacterCollection(this); }

public string Text { get { return new string(TextArray); } } }

class Test { static void Main() { Document d = new Document("peter piper picked a peck of pickled peppers. How many pickled peppers did peter piper pick?");

// Change word "peter" to "penelope": for(int i= 0;i<d.Words.Count;i++) { if(d.Words[i] == "peter") d.Words[i] = "penelope"; }

// Change character "p" to "P" for(int i=0;i<d.Characters.Count;i++) { if(d.Characters[i] == 'p') d.Characters[i] = 'P'; } Console.WriteLine(d.Text); } }