Topical Information

This program works with more data to give you some more practice at handling more variables. It will hopefully also give you an even better feel for how much testing is necessary to verify a program's correctness. Finally, it gives a refresher to some concepts from algebra.

Program Information

Write a program that helps the user calculate the midpoint of a line segment in the 2D Cartesian plane. Try to make your results as readable as possible.

As an example, you might have the program interaction look something like (the parts in this color are typed by the user):

$ ./midpoint.out

                 Welcome to the 2D Midpoint Program!!!

What is the first end-point?  3.4 12.2
What is the second end-point?  13.4 12.2

Thank you!!  Calculating...  Done.

The midpoint of the line segment between (3.4, 12.2) and (13.4, 12.2)
is (8.4, 12.2).

Thank you for using the TMP!!

Endeavor to have a voracious day!

$

Thought Provoking Questions

1. How many variables are needed here? (Hint: There are two points being input and a third point being output. How many values are needed to 'make' a 2D point?)
2. Would it make any sense to have whole-valued point coordinates (as opposed to decimal-valued point coordinates...)? That is, would it ever be correct for you to assume that a point's coordinates would never have fractional parts?
3. What is the formula to calculate a midpoint? Compare/Contrast the x part of the formula and the y part. (I.E. How are they similar? How are they different?)
4. What happens if the input points are in different quadrants? In the same quadrant? On an axis? At the origin? (I.E. Can your program ever go wrong because of the points' locations?)
5. How many different ways can you pick a pair of points from the Cartesian plane: quadrant(s), axis/axes, origin? (In other words, how many tests would it take to completely test your program?) (You do not have to script that many tests. But you should be able to calculate how many there should be. That way when you are working in industry, you can more thoroughly test your applications and run Micro-sloth out of business. *chuckle* *grin*)

This assignment is (Level 1.5).

Options

• Toward a More Natural Manner of Input

  Students are complaining that their teacher makes them use standard ordered pair notation for points in class, but your program makes them enter points without the notation. They are getting frustrated and some even confused.

  Add (Level 1) to force the user to enter the end points of the segment in normal, ordered-pair style (with parenthesis surrounding the coordinates and a comma between them).

  The program interaction might now look something like (the parts in this color are typed by the user):

  $ ./midpoint.out
  
                   Welcome to the 2D Midpoint Program!!!
  
  What is the first end-point?  (3.4, 12.2)
  What is the second end-point?  (13.4, 12.2)
  
  Thank you!!  Calculating...  Done.
  
  The midpoint of the line segment between (3.4, 12.2) and (13.4, 12.2)
  is (8.4, 12.2).
  
  Thank you for using the TMP!!
  
  Endeavor to have a voracious day!
  
  $
  

  More Thought Provoking Questions

  1. To make the input style more natural, you'll need to make the user type in the parentheses and the comma for typical Cartesian point notation. What [data] type of variable(s) will this require?
  2. How many variables will you need to make the input style more natural for the user? At minimum? At most?
  3. How can the parentheses and comma be placed right next to the numbers like that? How can cin determine where the number stops and the other stuff begins? Remember what happened when you typed a symbol or letter at a numeric prompt before? It was chaos! Why don't we see those problems here?
  4. What happens if the user doesn't type the parentheses or the comma? What happens if they type some other symbols instead? Letters instead? Digits instead? (Try input like: $4^5% and see what happens. Try 44 12x — what happens? Experiment...) (Do not try to correct this behavior — just document it.)
  5. What if everything they type is non-numeric (i.e. '&*$#^')? Remember what happened when you typed a symbol or letter at a numeric prompt before? (Again, do not try to correct this behavior — just document it.)

Total Level Possible

If you did all above options, this lab could be worth as much as (Level 2.5).