opEmpty.m

classdef opEmpty < opSpot
%OPEMPTY   Operator equivalent to empty matrix.
%
%   opEmpty(M,N) creates an operator corresponding to an empty M-by-N
%   matrix. At least one of M and N must be zero.

%   Copyright 2009, Ewout van den Berg and Michael P. Friedlander
%   See the file COPYING.txt for full copyright information.
%   Use the command 'spot.gpl' to locate this file.

%   http://www.cs.ubc.ca/labs/scl/spot
    
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    % Methods - Public
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    methods
        
       %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       % Constructor
       %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       function op = opEmpty(m,n)
          if nargin ~= 2
             error('Exactly two operators must be specified.')
          end
          
          if ~((m == 0) || (n == 0))
             error('At least one dimension must be zero.')
          end
            
          op = op@opSpot('Empty',m,n);
       end % Constructor

       %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       % Double
       %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       function A = double(op)
          A = [];          
       end       
       
    end % Methods
    
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    % Methods - protected
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    methods( Access = protected )
       
        % Multiplication
        function y = multiply(op,x,mode)
           if (mode == 1)
              y = zeros(op.m,0);
           else
              y = zeros(op.n,0);
           end
        end % Multipy
      
    end % Methods
        
end % Classdef