% MatLab function for part 3 of the question for the CSC 336 tutorial
% on 29 Sept. 2007.
%
% This function approximates e^x by summing the series
%      sum = 1 + |x| + |x|^2/2! + |x|^3/3! + ...
% from left to right until the value of the sum does not change
% and then setting the apprxomiation to e^x to sum if x >= 0 or 
% or 1/sum if x < 0.
%
%					K.R.J.    24 Sept. 2007

function y = exp2(x)
   
   sumold = 0;
   sum = 1;

   xabs = abs(x);

   k = 0;
   term = 1;	% term will be |x|^k/k!  We increment each time around the
                % while look to avoid having to recompute |x|^k/k!

   while sumold ~= sum,
      sumold = sum;
      k = k+1;
      term = term * xabs / k;
      sum = sum + term;
   end

   if x >= 0 
      y = sum;
   else
      y = 1/sum;
   end