%-------------------------------------%
% Homework 6: Problem 3               %
% Date: 10/22/2002                    %
%                                     %
% Gun Srijuntongsiri                  %
% gs61                                %
% ??????                              %
%-------------------------------------%

% Variables
% ---------
%   signChange = number of sign changes
%   curNum     = current number being inputted
%   prevNum    = last number before the current number in the sequence.

signChange = 0;

% Ask for first number,
curNum = input('Enter a number: ');
prevNum = curNum;

% If the first number is in range, ask for the second.
if curNum >= -100 & curNum <= 100
    curNum = input('Enter a number: ');
end

% While the number is in range,
while curNum >= -100 & curNum <= 100
    % If change sign, then the product of two numbers is either negative,
    %   or zero where the two numbers are not both zeros at the same time.
    if (curNum*prevNum < 0) | (curNum*prevNum==0 & curNum~=prevNum)
        signChange = signChange+1;
    end
    prevNum=curNum;                       % change previous number
    curNum = input('Enter a number: ');   % and ask for new number
end

% Display the result
disp(['The number of sign changes is ', num2str(signChange),'.']);