CSE 326, Data Structures
Project2: Text Editor

• GPKernel.h, GPkernel.c - you may be familiar with these from CSE143. These files provide utilities for easily opening X windows, drawing text, and handling input. You do not need to modify these files in any way.


• simpleX.h simpleX.C - more specific X windows functions and constants which are handy for this assignment. You won't need to modify these at all either.


• editor.h editor.C - the driver program that mediates between the user and the Text class. Again, you should not need to modify these at all.


• Makefile - make editor will build your program


• Text.h, Text.C - these contain a skeleton of the specification and implementation of the Text and iterator ADT. Although there are quite a few functions that you will need to flesh out, many of them are quite simple, so don't be overwhelmed by the number of functions that you need to implement.
  You will need to implement the internal representation of the text, and implement the following functions.
  
  Functions from the Text class:
  • Text()
    The Text default constructor creates itself as an empty text document containing only the end-of-text character.
  
  
  • ~Text()
    The Text destructor deallocates all of the memory that was used for storing the text document.
  
  
  • iterator begin()
    The begin method returns an iterator that points to the first character in the document. (There will always be a first character since every document contains at least the end-of-text character.)
  
  
  • erase(iterator& iter)
    The erase method deletes the character before the one pointed to by iter.
  
  
  • iterator create_iterator(int row)
    The create_iterator method returns an iterator that points to the first character of the given row. If the row given does not exist (because there are not that many rows in the document) the operation is undefined. This is called by the screen drawing routine as it updates the screen
  
  
  • iterator create_iterator(int column, int row)
    This create_iterator method returns an iterator that points to the character whose row and column numbers are the values given if such a character exists. If the row given does not exist, then the iterator should be on the last row. If the column given does not exist, the iterator should point to the last character on that row. This is called by the driver in response to mouse clicks, arrow key presses, et al.
  
  
  • insert(iterator& iter, char ch)
    The insert method inserts the given character before the one pointed to by iter. Because insert places the new character before the one pointed to by iter, it is not possible, without some shenanigans, to insert characters at the end of the file. Our trickery will be to add a special end-of-text after the last "real" character in the file. An iterator will be allowed to point to the end-of-text characters, and thus, insert characters after the last real character. The end-of-text character will be set up initially as the last character in the text document, and since it is not possible to insert after the end-of-text character (for the same reason that it was not possible to insert after the real last character before), the end-of-text character will remain at the end.
  
  
  • bool is_eot(iterator& iter)
    The is_eot method returns true if the given iterator points to the end-of-text character.
  
  
  • void long_delete(iterator& iter1, iterator& iter2)
    The long_delete method works as follows. Let L be whichever of the two given iterators points closer to the beginning of the document, and let R be the other one. Then, the long_delete method deletes all of the characters starting from the one pointed to by L, up to, but not including, the one pointed to by R.
  
  
  
  Functions from the iterator class.
  • iterator()
    The iterator default constructor creates an iterator that does not point to any character in the text. It is the iterator equivalent of the null pointer. Attempting to dereference this iterator is an undefined operation.
  
  
  • iterator(const iterator& iter)
    The iterator copy constructor creates an iterator that is a copy of the given iterator.
  
  
  • ~iterator()
    The iterator destructor can do any necessary cleanup.
  
  
  • iterator operator++(int)
    iterator operator--(int)
    The (postfix) ++ and -- operators treat the text document as one long string of characters (including newlines). The ++ operator makes the iterator point to the next character in the document, and the -- operator makes the iterator point to the previous character in the document. If there is no next or previous character, respectively, these operations should make the iterator be equal to the iterator returned by the default constructor above.
  
  
  • iterator operator=(const iterator& iter)
    (assignment operator) Make this iterator point to the same character as itr. Then return a copy of iter.
  
  
  • bool operator==(const iterator& iter)
    (equals operator) Return true if this iterator points to the same place as iter.
  
  
  • char operator*()
    (dereference operator) Return the character that this iterator points to. Lets us treat the iterator like a pointer.
  
  
  • int row()
    column() const
    The row and column methods treat the text document as a 2-dimension arrangement of characters. All rows other than the last row of the document, end with a newline character. Row 0 consists of all of the text up to and including the first newline character; Row 1 consists of all of the characters after the first newline character, up to and including the second one; and so on. In each row, the first character is in column 0, the second one is in column 1, and so on. The row method returns the row number of the character that the iterator points to, and the column method returns the column number of the character that the iterator points to. Note that these row and column numbers should be allowed to become as large as memory allows.
  
  

• create_iterator(int row) is important because the screen drawing routine uses this to get an iterator to the start of the line of text. Since this happens a lot, it should not be slow.
• insert(iterator& iter, char ch) needs to be fast because it is used very frequently to insert characters when typing and when loading a file
• create_iterator(int column, int row) is important when handling mouse clicks, and for the up and down arrows.
• row(), column() should be quick because they are used often by the driver in all sorts of situations.

• Text.h, Text.C
• README - This is a text file describing your project implementation. It should describe your choice of data structure for the Text ADT. In particular, answer the following questions:
  • Describe your choice of data structure for the Text ADT.
  • Describe at least one other data structure that you could have used to implement the Text ADT. Explain why you choose your data structure instead of the other(s)? What was your main criterion for evaluating which data structure you picked?

% cd ~/326stuff/myproj2dir
% make clean
% cd ../
% turnin -c cse326=AA -p project2 myproj2dir