HAS_PARALLEL_TOOLBOX does the user have Parallel Computing Toolbox and the license available for it?

This deliberately doesn't catch the case where the toolbox and license is valid, but there aren't enough licenses, so that the user knows what's happening. The user can use stdlib.checkout_license() to affirm that the license is available at the time of the call.

function y = has_parallel_toolbox()

try
  gcp('nocreate');
  y = true;
catch e
  if e.identifier ~= "MATLAB:UndefinedFunction"
    rethrow(e)
  end
  y = false;
end

end