Project 12 Extra Notes

Recursive Functions

I'd have one main recommendation: use wrapper functions. It's also possible to do the work without multiple functions, but things are more likely to go wrong or get really weird. Some hints:

1. Decide what needs to be done only once per function call. This work goes in the wrapper (user-callable) function, such as sine().
2. Where the repeated calculation begins, call the recursive function with the appropriate initial parameters. So sine() can call sine_rec(), for example. This will be declared in the .cpp file rather than the .h file.
3. Things that change between recursive calls should probably be parameters. Global variables might also work, but as mentioned in the project notes, they should not be used to exchange information between functions. If you go the parameter route then default parameters may be useful. You may also need parameters for values that do not change between recursive calls (but are parameters to the wrapper function).
4. The recursive function will call itself until it reaches a base case, at which point it starts returning. Think about what to do to get from one step to the next. When the function decides that the current call is not a base case, it needs to take the return value of the recursive call and do something with it, then return the new value.

Misc.

Don't start by copying everything from the Project 5.  Look at your scoresheet first and make sure you don't repeat any mistakes in the library or the driver. Open your old library alongside the new one, and copy bits of code if needed. You need factorial() and power() to work before you can do sine() and cosine().

If you had good test cases last time, you will be able to recycle most of it. You might also want to give auxiliary testing functions a try, if you didn't last time. Note that your functions will probably hang or crash on smaller input values this time (remove those tests).

Last, a warning: do not try turning in your old iterative functions. If you do, you might get a negative score.