% MT 03 2018/19
% Challenge: Find the error in this code!

fprintf ( '  Create a -1, 2, -1 tridiagonal matrix.\n ' );
fprintf ( '  Compare with the MATLAB online reference for "if, elseif, else". Find the error. \n ' );

  m = 4;
  n = 6;
  a = zeros ( m, n );

  % Expected result:
  %     2 -1  0  0  0  0
  %    -1  2 -1  0  0  0
  %     0 -1  2 -1  0  0
  %     0  0 -1  2 -1  0
  
  
  for i = 1 : m
    for j = 1 : n

      value = 0.0;
      
      if ( j == (i - 1) || j == (i + 1) )
        value = - 1.0; 
      elseif ( j == i )  % Wrong Syntax here opens a new if-block!!!
        value = 2.0;
      else
        value = 0.0;
      end

      a(i,j) = value;

    end
  end

  a

  return % leaves if-block too early!
  %end   Unneccesary