You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: subsref.m
    path of file: ./repos/chebfun/@diskfun
    
    the code of the file until where you have to start completion: function varargout = subsref(f, index)
%SUBSREF   DISKFUN subsref.
%( )
%   F(TH, R, 'polar') returns the values of the DISKFUN F evaluated at the
%   value(s) (TH, R) in polar coordinates. See CHEBFUN/FEVAL for
%   further details.
%
%   F(:, R) returns a chebfun representing the function F along a radial
%   slice fixed by R, and F(TH, :) returns a chebfun representing F along 
%   an angular slice. 
%
%   F(:, :) returns F.
%
%   F(X, Y) or F(X,Y, 'cart') returns the values of the DISKFUN F evaluated 
%   at the value(s) (X,Y) in Cartesian coordinates. 
%   The colon operator for Cartesian coordinates is not supported, 
%   except for F(:, :), which just returns F.
%
%   F(c) where c is a complex-valued chebfun evaluates F along the contour
%   parametrized by the real and imaginary parts of c, and returns a 
%   chebfun representing the values of F along the contour.
% 
%   F.PROP returns the property PROP of F as defined by GET(F, 'PROP').
%
% {}
%   F{S1, S2, S3, S4} restricts F to the domain [S1, S2, S3, S4]. See
%   SEPARABLEAPPROX/RESTRICT for further details. Note that 
%   F{[S1,S2, S3, S4]} is not supported due to the behaviour of the MATLAB 
%   subsref() command.
%
% See also DISKFUN/FEVAL, DISKFUN/GET and DISKFUN/RESTRICT.

% Copyright 2017 by The University of Oxford and The Chebfun Developers.
% See http://www.chebfun.org/ for Chebfun information.

idx = index(1).subs;

% Check for the cases that must be explicitly handled here, which are
% 1. f(x, y), x, y are numeric, cartesian flag.
% 2. f(t,r) t, r are numeric, polar flag.
% Pass the other cases off to separableApprox/subsref.

if ( strcmp(index(1).type, '()') )
    x = idx{1};
    if ( length(idx) == 3 ) && (strcmp(idx{3}, 'polar'))
        y = idx{2};
        out = feval(f, x, y, 'polar');
        varargout = { out };

    
function varargout = subsref(f, index)
%SUBSREF   DISKFUN subsref.
%( )
%   F(TH, R, 'polar') returns the values of the DISKFUN F evaluated at the
%   value(s) (TH, R) in polar coordinates. See CHEBFUN/FEVAL for
%   further details.
%
%   F(:, R) returns a chebfun representing the function F along a radial
%   slice fixed by R, and F(TH, :) returns a chebfun representing F along 
%   an angular slice. 
%
%   F(:, :) returns F.
%
%   F(X, Y) or F(X,Y, 'cart') returns the values of the DISKFUN F evaluated 
%   at the value(s) (X,Y) in Cartesian coordinates. 
%   The colon operator for Cartesian coordinates is not supported, 
%   except for F(:, :), which just returns F.
%
%   F(c) where c is a complex-valued chebfun evaluates F along the contour
%   parametrized by the real and imaginary parts of c, and returns a 
%   chebfun representing the values of F along the contour.
% 
%   F.PROP returns the property PROP of F as defined by GET(F, 'PROP').
%
% {}
%   F{S1, S2, S3, S4} restricts F to the domain [S1, S2, S3, S4]. See
%   SEPARABLEAPPROX/RESTRICT for further details. Note that 
%   F{[S1,S2, S3, S4]} is not supported due to the behaviour of the MATLAB 
%   subsref() command.
%
% See also DISKFUN/FEVAL, DISKFUN/GET and DISKFUN/RESTRICT.

% Copyright 2017 by The University of Oxford and The Chebfun Developers.
% See http://www.chebfun.org/ for Chebfun information.

idx = index(1).subs;

% Check for the cases that must be explicitly handled here, which are
% 1. f(x, y), x, y are numeric, cartesian flag.
% 2. f(t,r) t, r are numeric, polar flag.
% Pass the other cases off to separableApprox/subsref.

if ( strcmp(index(1).type, '()') )
    x = idx{1};
    if ( length(idx) == 3 ) && (strcmp(idx{3}, 'polar'))
        y = idx{2};
        out = feval(f, x, y, 'polar');
        varargout = { out };
        
    elseif ( length(idx) == 3 ) && (strcmp(idx{3}, 'cart'))
        y = idx{2};
        out = feval(f, x, y, 'cart');
        varargout = { out };
        
    else  % Pass to separableApprox.
        out = subsref@separableApprox(f, index);
        varargout = { out };
    %else
      % error('CHEBFUN:DISKFUN:subsref:inputs', ...
               % 'Can only evaluate diskfuns at (X,Y) or (TH,R)');    
    end