Week 05 Notes for CS 2500, Section 001 -- Fall 2003

• Take roll.
• Announcement(s)
  
  
  • The third programming assignment is in the web directory now. Let's get started on that. The first due date is 10/10.
    
    
  • I will be at a conference on Oct 8 and 10. Let's discuss the possibility of you meeting in the lab on those days and working on the level two program in teams. Let's also discuss the possibility of e-mail questions during my absence.
    
    
  • Reserve enough time before you need to turn in an assignment to go back to the specs and the general directions for submissions, read them, and make sure you have done everything you were asked. Let there be no hard feelings if I take off significant amounts of points for things you may have thought were insignificant. Look at the comments you get back with your program #1 score sheet. You can lose points on the next program if I don't see improvements resulting from my comments.
    
    
  • I am about done correcting program #1 -- will work on some late submissions.
    
    
  • Send me a 5-digit code if you want me to post your grades.
    
    
  • This week in Carrano we finish reading appendix A and start chapter 3 (data abstraction). In Anderen we read chapters 8-9 (directories and file manager). The sorting program is due on Friday.
    
    
• Discuss the sorting program. This function:

  
  void sort (int list[MAX_ELTS], int first, int last)

  can operate like this: IF (first < last)
  1. find the index of a smallest element X between indices 'first' and 'last'
  2. Swap X with the element at index = 'first'
  3. recursively sort the list from index 'first+1' to index 'last'
  
  
• The discussion above tells you about all you need to know to write a recursive "sort" function for programming assignment #2 -- if you know how to code the step of finding the smallest element.
  
  
• The heading for a function that finds the smallest element in a segment of an array could look like this:

  
  int minLoc(int list[MAX_ELTS], int first, int last) 

  It could operate like this:

  
      assign: minLocation <-- first ;
      FOR each index j first+1 to last
          IF list[j] is smaller than list[minLocation]
          THEN assign minLocation <-- j
      RETURN minLocation 
  

• The idea above for minLoc is an iterative function. If you want to you can write a recursive minLoc function, but that's an 'extra challenge' and it is not necessary.
  
  
• When you write your code be careful to keep straight in your mind which variables represent array indices and which represent array elements. for example, the job of function "minLoc" is to return the array index of a smallest element in a section of the array. Function minLoc is not supposed to return the value of a smallest element. Another example: when your program calls function "swap" it should make a call sort of like this: swap (list[a], list[b]) but not like this: swap(a,b). (It is not appropriate to give array indices as the parameters to swap.)
  
  
• Finish up going over answers to questions on the quiz?
  
  
• We can discuss searching an array for a value as a counterpoint to the minLoc function.
  
  
• C++ classes give us a way to implement abstract data structures. We can organize different kinds of groupings of data elements and place the operations we want to perform on the data in the same container that holds the data.
• C++ classes allow us to hide implementation details from the clients of the class. This assures us we can change implementation details just by making changes to the class definition. The rest of the program will work with the new class.
• Examine the ListA.h and ListA.cpp class code and write some sample code to use a list.