function factorthis(n)
% help for factorthis(n)
% copyright 1998, D. Estep
%
% PURPOSE
%
% this function computes all the integer factors of the input integer n.
%
% FUNCTION STATEMENT 
%   
% factorthis(n)
%
% REQUIRED VARIABLES
%
% n
%
% USAGE
%
% >>factorthis(integer)

% Author: Don Estep
% Date:   11/24/98

% first check to make sure that n is an integer. we use the
% floor command, which rounds down to the nearest integer

if (floor(n) ~= n) 
   % the comparision ~= means not equal
   disp('input integers please!')
   break
   % this break will halt execution of the function
end

disp('now factoring')

m = floor(sqrt(n));
% m is the largest integer we have to test

for i = 1: m
   
   j = floor(n/i);
   % divide n by i and then round down to get j
  
   
   if (j*i == n)
      % j*i = n means a perfect factor
      fprintf('found factors %d and %d\n',i,j)
      % We use a more sophisticated print statement.
      % fprintf( ) prints what is inside the ( ).
      % In this case we say to print the set of characters
      %          found factors <number> and <number>
      %   the "\n" means go to the next line
      % We use %d to denote the location and format of the numbers to
      % be printed. For each %d% we should follow with a variable.
      % Here we insert the value of i for the first %d and j for the second.
      %   %10.5e would print the numbers in exponential format using
      %          10 digits total with 5 following the decimal point
      %   %10.5f prints the numbers in floating format using 10 digits
      %          total and 5 following the decimal point
      
      
   end
   
end      
%output
%>>factorthis(10203032100)
%now factoring
%found factors 1 and 1.020303e+010
%found factors 2 and 5.101516e+009
%found factors 3 and 3.401011e+009
%found factors 4 and 2.550758e+009
%found factors 5 and 2040606420
%found factors 6 and 1700505350
%found factors 10 and 1020303210
%found factors 12 and 850252675
%found factors 15 and 680202140
%found factors 20 and 510151605
%found factors 25 and 408121284
%found factors 30 and 340101070
%found factors 50 and 204060642
%found factors 60 and 170050535
%found factors 75 and 136040428
%found factors 100 and 102030321
%found factors 150 and 68020214
%found factors 300 and 34010107