Clarifications for hwk1
-----------------------

A k-decision list is a decision list where each test is a conjunction
of up to k literals.  E.g., a 2-decision list might look like:

      if (x_1 = 1 and x_3 = 0) then +
 else if (x_2 = 0 and x_3 = 1) then -
 else if (x_2 = 1 and x_4 = 0) then -
 else +

(this was mentioned briefly in the notes for lecture 1).