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: all.m
    path of file: ./repos/chebfun/@chebfun
    
    the code of the file until where you have to start completion: function a = all(f)
%ALL   True if all values of a CHEBFUN are nonzero.
%
% See also ANY, ISZERO.

    
function a = all(f)
%ALL   True if all values of a CHEBFUN are nonzero.
%
% See also ANY, ISZERO.

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

% Check the piont values first (as this is trivial):
tol = vscale(f)*eps;
a = all(abs(f.pointValues) > tol);

% Check to see if there are any roots:
if ( any(a) )
    r = roots(f, 'nojump');
    if ( isempty(r) )
        return
    end