opInverse.m

%opInverse   (Pseudo) inverse of operator
%
%   Ainv = opInverse(A) creates the (pseudo) inverse of a M-by-N
%   operator A. The product Ainv*b is then equivalent to A\b.
%
%   See also @opSpot/mldivide.

%   Copyright 2009, Ewout van den Berg and Michael P. Friedlander
%   http://www.cs.ubc.ca/labs/scl/sparco
%   $Id$

classdef opInverse < opSpot

    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    % Methods
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    methods

       %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       % Constructor
       %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       function op = opInverse(A)
          
          if nargin ~= 1
             error('Exactly one operator must be specified.')
          end
           
          % Input matrices are immediately cast as opMatrix's.
          if isa(A,'numeric'), A = opMatrix(A); end
          
          % Check that the input operators are valid.
          if ~isa(A,'opSpot')
             error('Input operator is not valid.')
          end
          
          % Construct operator
          [m, n] = size(A);
          op = op@opSpot('Inverse', n, m);
          op.cflag      = A.cflag;
          op.linear     = A.linear;
          op.children   = {A};
       end
      
       %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       % Display
       %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       function str = char(op)
          str = ['inv(', char(op.children{1}) ,')'];
       end
       
    end % Methods


    methods ( Access = protected )
       %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       % Multiply
       %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       function y = multiply(op,x,mode)
          opA    = op.children{1};
          if mode == 1
             A = opA;
          else
             A = opA';
          end
           y = A\x;
        end % Multiply

    end % Methods
   
end % Classdef