This is my version of the source code for this homework.

For those who wanted to compare results, here is what I have as the expected output for the four required problems and the extra credit.

• Best calendar month (% gain)

       Opening price on 1932/08/01 was 54.26.
       Closing price on 1932/08/31 was 73.16.
       That is a gain of 34.83%.
  

• Most consecutive days with gain

       Found 13 consecutive days of gain
       starting on 1987/01/02 and continuing through 1987/01/20.
  

• Biggest historical downturn (% loss)

       High price on 1929/09/03 was 386.10.
       Low price on 1932/07/08 was 40.56.
       That is 10.51% of the previous high.
  

• Year end analysis (geometric mean)

       Day type          Geometric Mean
       -------------     --------------
       first of year           1.001118
       last of year            1.001787
       typical                 1.000119
  

• Daily analysis (geometric mean)

       Best historic date is 10/20 with geometric mean 1.005743.