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    function varargout = dtffir(varargin)
%DTF Direct-form transfer function FIR filter virtual class.
%   DTFFIR is a virtual class---it is never intended to be instantiated.
  
%   Author: Thomas A. Bryan
%   Copyright 1988-2003 The MathWorks, Inc.

error(message('signal:dfilt:dtffir:dtffir:SigErr'));