diff -r ff8d075842d5 -r 28c8e17ab83a progs/drumb_sol.scala
--- a/progs/drumb_sol.scala	Thu Dec 01 22:08:00 2016 +0000
+++ b/progs/drumb_sol.scala	Fri Dec 02 16:45:31 2016 +0000
@@ -45,7 +45,7 @@
 val p_fb = get_prices(List("FB"), 2012 to 2014)
 val p = get_prices(List("GOOG", "AAPL"), 2005 to 2012)
 
-get_prices(List("BIDU"), 2004 to 2008)
+val tt = get_prices(List("IBM", "BIDU"), 2004 to 2008)
 
 // (2) The first function below calculates the change factor (delta) between
 // a price in year n and a price in year n+1. The second function calculates
@@ -65,7 +65,7 @@
 
 // test case using the prices calculated above
 val d = get_deltas(p)
-
+val ttd = get_deltas(tt)
 
 // (3) Write a function that given change factors, a starting balance and a year
 // calculates the yearly yield, i.e. new balanace, according to our dump investment 
@@ -85,6 +85,16 @@
   }
 }
 
+yearly_yield(ttd, 100, 0)
+yearly_yield(ttd, 100, 1)
+yearly_yield(ttd, 100, 2)
+yearly_yield(ttd, 100, 3) assert((yearly_yield(ttd, 100, 0) - 107).abs <= 2)
+  assert((yearly_yield(ttd, 100, 1) - 85).abs <= 2)
+  assert((yearly_yield(ttd, 100, 2) - 156).abs <= 2)
+  assert((yearly_yield(ttd, 100, 3) - 210).abs <= 2)
+
+
+
 //test case
 yearly_yield(d, 100, 0)
 yearly_yield(d, 225, 1)
@@ -116,6 +126,9 @@
 println("Real data: " + investment(rstate_portfolio, 1978 to 2016, 100))
 println("Blue data: " + investment(blchip_portfolio, 1978 to 2016, 100))
 
+
+investment(List("IBM", "BIDU"), 2004 to 2008, 100)
+
 val p_fb = get_prices(List("FB"), 2011 to 2016)
 
 // prices 2011 - 2016