%-------------------------------------%
% Homework 7: p.4                     %
% Date: 11/11/2002                    %
%                                     %
% Gun Srijuntongsiri                  %
% gs61                                %
% ??????                              %
%-------------------------------------%

% Variables:
%   str   = user inputted string
%   shift = number of shifts

% Ask for the string and shift
str = input('Enter a string to be encrypted: ','s');
shift = input('How many to shift? ');

str = lower(str);   % Change to lowercase
disp(['Original string (converted to lowercase): ',str]);

% Shift one character at a time, from the first to the last
for i=1:length(str)
    
    % Shift to the left by $shift$ amount
    str(i)=char(str(i)-shift);
    
    % Now taking care of rollover from 'a' back to 'z'
    if str(i) < 'a'
        str(i) = char(str(i)+'z'-'a'+1);
    end
end

% Output the shifted result
disp(['Encrypted string                        : ',str]);