WorkSheet #2 - Focusing on Conditionals (if/else)

1) Create a new project and cpp file in your environment. You should
   be able to do this quite easily at this point without referring to
   notes. If you're still struggling there, it means you need to
   practice much more to catch up. Remember to compile often and to
   test in pieces.

2) This work sheet will focus on using if and if/else
   expressions. Using the variables from the first worksheet (they
   will be repeated here) write if expressions to make sure that
   values were entered correctly. If they were not correct, feel free
   to fix them automatically for now. (Later we'll learn how to bug
   the user to give us a proper value).

   Attributes: name, age, height, weight, shoe size, employment
   status, number of courses taken, number of credit hours taken,
   current GPA

   Example: for weight. We're going to assume that weights are in
   pounds and that valid weights are in the range 0 pounds to 4000
   pounds for a human. We've chosen weights to be stored as integers,
   although we could consider float and double to be valid choices if
   we wanted to allow weights with decimal places.

   int weight;
   cout << "Please enter your weight in pounds: ";
   cin >> weight;
   cout << "You have entered " << weight << " pounds." << endl;
   if(weight < 0) { //then this weight is invalid
      cout << "Weight is below 0. IMPOSSIBLE! Weight is now 0." << endl;
      weight = 0; //I've "automatically" corrected this value.
   } 
   if(weight > 4000) { //then this weight is still invalid!
      cout << "Weight is above 4000. Weight is now 4000." << endl;
      weight = 4000;
   }
   cout << "Weight is now " << weight << " pounds." << endl;

   //there are also ways to string ifs together and use AND/OR boolean logic


3) When you've satisfied yourself that all values are being handled
   with errors, make a new check at the end of your code relating to
   cin.fail(). If you get to the end of your code and cin has failed,
   then it means some of the variables were not read in by cin. It
   would look something like this:

   if( cin.fail() ) {
     cout << "Input failed. Remaining output is erroneous" << endl;
   }

4) Lastly, we make a bunch of cout statements to turn this assignment
   into a story. After I entered some information the final story
   might say the following:
   
   Doc is using this program. Doc is 12 years old, 37 pounds, and
   stands only 23 inches tall. Doc wears a size 2 shoe. Doc has no
   employment, 0 courses taken, 0 credit hours taken and a 4.0
   GPA. Way to go Doc.



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Preparing for the final project!

Last time you were told that your final project would have some sample
variables and values. That list is repeated below. To prepare for the
final project, you can make several tests for proper input. Total
mass, fuel mass and ISP can never be below 0. Also, total mass must be
larger than fuel mass. Write some if statements to protect these
values such that they never get to the bottom of the code in an
erroneous state. Write down any assumptions or decisions you make when
you complete this process.


 -craft name   	      	   	ex: Challenger
 -total mass			ex: 1995806.42
 -fuel mass  			ex: 1671487.88
 -ISP				ex: 180.3
 -gravity a constant value at 9.80665