%%%%%% 
  %  Script file: funxy.m 
  % 
  %  Purpose: 
  %    This program solves the function f(x,y) for a 
  %    user-specified x and y, where f(x,y) is defined as: 
  %                 _ 
  %                | 
  %                | x + y             x >= 0 and y >= 0 
  %                | x + y**2          x >= 0 and y < 0 
  %       f(x,y) = | x**2 + y          x < 0  and y >= 0 
  %                | x**2 + y**2       x < 0  and y < 0 
  %                |_ 
  % 
  %  Record of revisions: 
  %      Date       Programmer          Description of change 
  %      ====       ==========          ===================== 
  %    12/05/98    S. J. Chapman        Original code 
  % 1. 02/05/00    S. J. Chapman        Modified for nested ifs 
  % 
  % Define variables: 
  %   x     -- First independent variable 
  %   y     -- Second independent variable 
  %   fun   -- Resulting function 

  % Prompt the user for the values x and y 
  x = input ('Enter the x coefficient: '); 
  y = input ('Enter the y coefficient: '); 
    
  % Calculate the function f(x,y) based upon 
  % the signs of x and y. 
  if x >= 0 
     if y >= 0 
        fun = x + y; 
     else 
        fun = x + x^2; 
     end 
  else 
     if y >= 0 
        fun = x^2 + y; 
     else 
        fun = x^2 + y^2; 
     end 
  end 

  % Write the value of the function. 
  disp (['The value of the function is ' num2str(fun)]);