Homework 3, Feedback and Testing

• You can check your program on cslab103 by running my test script

  • ~dbennett/130/program3/doit yourProgramName
    

  • This will run your program a number of times. The output will look like this:

  • Checking against datfile 00Default1
    100
    Moon
    
            The correct answer is  New Weight: 16.6000
            The program produced   New Weight: 16.6000
    
    Press enter to continue
          

  • The first line is the name of the test file used.
  • The next two lines are the contents of this file.
  • The last part of the next two lines should match. If it does not, your program has a problem.
• Some feedback
  • Your program should print the result to four decimal places.
    • setprecision() behaves differently for scientific and fixed.
    • I always use cout << fixed << setprecision(n)
    • In any case, you should print four decimal places.
  • Constants
    • Local convention says to declare them globally
    • And UPPER_CASE_WORDS
    • and not MARS="Mars"
  • Getting small details right.
    • The spec said that your weight should be proceeded by "New Weight: "
    • And that errors should be labeled "unknown"
    • I used these in my test script to check for correctness.
    • If you did not produce these, you are not right.
  • Variables
    • Local convention says to declare these at the beginning of each routine.
    • And use reasonable names.
    • And use variableNameCase
    • Only declare the variables you need.
      • destinationPlanetWeight, not mercuryWeight, marsWeight,...
    • But do declare variables if you need them.
  • Computations
    • Only do the computation you need.
      • Don't compute the weight on all planets, just the one you need.
    • Eliminate duplicate code.
      • This is bad

      • if (destPlanetName == MERCURY_NAME) {
             endWeight = startWeight * MERCURY_FACTOR;
             cout << fixed << setprecision(5) ;
             cout << "New Weight: " << endWeight << endl;
        } else if (destPlanetName == VENUS_NAME) {
             endWeight = startWeight * VENUS_FACTOR;
             cout << fixed << setprecision(5) ;
             cout << "New Weight: " << endWeight << endl;
        } else if (destPlanetName == EARTH_NAME) {
             endWeight = startWeight * EARTH_FACTOR;
             cout << fixed << setprecision(5) ;
             cout << "New Weight: " << endWeight << endl;
        ...
        } else {
             cout << "New Weight: " << "unknown" << endl; 
        }
        

      • Move the cout statements to before and after the block.

      • cout << fixed << setprecision(5) ;
        if (destPlanetName == MERCURY_NAME) {
             endWeight = startWeight * MERCURY_FACTOR;
        } else if (destPlanetName == VENUS_NAME) {
             endWeight = startWeight * VENUS_FACTOR;
        } else if (destPlanetName == EARTH_NAME) {
             endWeight = startWeight * EARTH_FACTOR;
        ...
        } else {
              error = true;
        }
        
        cout << "New Weight: "
        if (not error) {
            cout << endWeight << endl;
        } else {
            cout << "unknown" << endl;
        }
                            

      • I would move the computation out as well.

      • float conversionFactor{0}
        
        cout << fixed << setprecision(5) ;
        if (destPlanetName == MERCURY_NAME) {
             conversionFactor = MERCURY_FACTOR;
        } else if (destPlanetName == VENUS_NAME) {
             conversionFactor = VENUS_FACTOR;
        } else if (destPlanetName == EARTH_NAME) {
             conversionFactor = EARTH_FACTOR;
        ...
        } else {
              error = true;
        }
        
        endWeight = startWeight * conversionFactor;
        
        cout << "New Weight: "
        if (not error) {
            cout << endWeight << endl;
        } else {
            cout << "unknown" << endl;
        }